I don't think that your drawings are looking very flat. the construction looks solid for me. If you want improving your illusion of 3D maybe study rendering (aka how light affect the form, I really like: https://www.amazon.de/gp/product/1933492961/ref=ox_sc_act_title_1?smid=A3JWKAKR8XB7XF&psc=1), but again. In this drawing the rendering looks fine.

clean and good understanding of 3d space

Hey, @James Mayr! It’s good to hear from you again! It’s awesome that you were able to join a life drawing class. Drawing from life is a whole new way of studying the figure, it puts a lot of our knowledge into context and adds a bunch of new challenges to our practice. It’s usually a lot of fun too. Hope you enjoyed your experience! I believe the difficulty you mentioned and your drawings themselves relate to the same core issue: you might be focusing too much on contours. Sure we use lines to produce our drawings, but, in this type of anatomy study, it’s important that, in our minds, we don’t care too much about the lines themselves, and instead, visualize mostly the 3D forms that they represent. If this is already what you’re trying to do, let me add a new suggestion and we'll see if it helps: instead of naming your marks on the paper as LINES or CONTOURS, try using a more “3D-oriented nomenclature” such as EDGES, CORNERS, BORDERS, SURFACES, PLANES. For example: rather than referring to parts of your drawing as “this line” or “that contour”, think “this corner of the box”, “that edge of the plane”, “this border of the oval” for example. My hypothesis is that using these “3D-related names” might help trigger your brain to “think in 3D” more so than if you use terms such as “line” or “contour”, which are more relative to a 2D kind of representation. In the drawing practice, also remember to build your figure drawings with simple forms (spheres, boxers, cylinders), with that idea of construction and mannequinization in mind. See if you can draw as if you were sculpting. I did a quick sketch over one of your drawings to better illustrate what I mean. The 3D construction doesn’t have to be complicated or involve detailing - it can be just like a wooden mannequin. Then, on top of these basic forms, we could do the anatomical study of the specific muscle group we’re focusing on (in this case, the Rectus Adbominus), and leave all the rest of the body just simplified. Also, one thing to keep in mind when drawing the actual muscles: remember to always track the attachment points (origins and insertions) so you can study the anatomy with more accuracy. I think these would be my main recommendations for you right now. Hope this all makes sense and that it helps you. Let me know in case you need assistance with anything else. Best regards!

Hey @James Mayr, Nice work! I like the motion on these! A little suggestion, try closing the space between the ribcage and pelvis. It should only be around one hand width apart max (Try putting your own hand between the side of your ribcage an pelvis). To avoid over complicating it, I'd suggest practicing this on the robo-bean until your gotten the spacing down. Keep at it! :]

Hi @James Mayr! The subject of Anatomy is really cool, and it helps a lot to describe and give more emphasis to the story of your poses. In your drawings, I can see that you are struggling a little with your fundamentals, line quality, and describing volumes, to name a few. Before adding the anatomy, it is crucial to show the basic volumes you are going to place those muscles over. As Glenn Vilppu says, "draw over the surface," but to draw over the surface, you must have a surface. I suggest you draw simple shapes and give them volume. Once that is clear, add the anatomy on top. I think that will help you a lot in your process and speed up your learning curve in learning anatomy! Keep it up! The drawing journey has a lot of lovely traps. Avoiding falling into those traps differentiates how long it will take you to learn any specific topic. I hope this helps!