Hello, Abbey. I'm here to start filling your review request. I've read through both chapters one and two and will comment on them here. I will continue to read through at least chapter three and review that one as well. I'm focusing in mostly on your listed areas of concern, but I'm sure I'll throw in some other comments as well as I go :)
You mentioned that you like to take a more simple approach with your story telling and personally I think that's a great writing philosophy. Sometimes when we try and do too much with the language and descriptions, we loose the best part -- the story itself. Over the first two chapters, I feel like you achieved this goal well but without swinging too far and leaving nothing but the bare bones behind. In regards to description specifically, I thought the amount itself was fine in chapter one. The details you did include were the ones that were most important, namely that Carla physically resembles Lily. Chapter two was perhaps a little too light on the details. You have an advantage with the readers being able to picture the settings, knowing them from the books, but it's still important to look for ways to add something special/put your own stamp on the story. For example, do the hallways feel smaller to Carla, looking at them as a teacher instead of a student? Does the hooting of the owls remind her of summers at home, listening to the birds in the wood near her home? All details don't have to just be about what the character is looking at, wearing, smelling -- but their reactions to them and what they say about the character's personality, history, or feelings.
I would suggest also being careful of weak asides/generalities. Here's one example: "...even though they chatted a little too much and occasionally messed around a bit." Compare that to something like "...even though she had to tell them three times to quiet down and had already been forced to issue a detention when one precocious third-year tried to set his textbook on fire." Okay, that might not be the best sentence I've ever written, but I'm sure you get the point. Not only is the latter more specific, it conjures up actual mental images for the reader and the language is much more exact (no "a little too much" and "around a bit"). If you are going to go light on the detail, which is totally fine, make sure the ones you pick really convey something to the reader.
Moving on to characterization, I didn't feel that your characters were wooden at all. Actually, I thought you worked to inject a lot of emotion into the story already. Clearly Carla has stirred some feelings in Snape, and she in him. And I really liked Cummins. She was a nice contrast to Carla -- you could have even played up the loose-lipped old gossip angle a bit more just for fun. I think the thing that worked less for me in terms of the characters were how true the emotions felt in proportion to the situations they found themselves in. For example, in chapter one: "He had to use every ounce of his self-control to keep himself from grinning in triumph." Every ounce of self-control is a LOT of self-control to exert in this situation. Snape is mean and enjoys being thought of as mean, but the fact that he enjoyed his own displeasure so much didn't feel in line with the context of the scene. Another example from chapter two: You mention Carla not being able to think of anything else but Snape, yet she is in her very first day at a new job. It's hard to believe the only thing she can think of at the moment is Snape. I think your characters may feel more life-like to you (and maybe by extension less wooden) if you actually dial them back a bit, make their emotions and feelings a bit more multidimensional.
The last thing I'll touch on is flow since you mentioned that in your AoC. I didn't really see any problems here. You divide the chapters up by scene, which makes them easy to follow along with. And when you do move within a scene, the transitions work fine. If you are really worried about flow and looking to make the story as smooth as possible, you could consider keeping the point of view the same unless a change in REALLY needed. For example, you switch to Snape's POV at the end of chapter two. It's after a scene break so it isn't confusing for the reader or anything, but since the scene that follows happens so close on the heels of the scene above, which was in Carla's POV, I might have suggested combining the scenes and finishing the chapter through her eyes. There isn't anything in Snape's head at that exact moment we just have to know to understand what's going on.
Okay, well that's all the notes I made on the first two chapters. I hope I was able to offer you some helpful comments on your areas of concern. I think this story is off to a very nice start. I feel like you're already dropping great hints at what is to come, and I like that the time-frame of this story is a bit different from what I normally see. It's not really a traditional Marauder-era story, but it also isn't Hogwarts-era either. There aren't as many well-planned pre-Hogwarts era stories out there, so extra bonus points for trying something a bit different! Thanks for sharing your story. I'll post another review soon!
Author's Response: Woah, that's a lot to take in, but thank you so much for the review!
I'll really try and take into account what you said about the descriptions and linking them to the character's history and feelings and such, and also about the sometimes over-dramaticness of my characters. It's something I do which I know I'm doing but can't even help, so I'm gonna try and make their feelings a bit more multidimensional too like you said.
Thank you so much again, this is really helpful. :)