I've pored over forums, youtube videos, anything to help me learn this feature. So please don't immediately smite me if you feel this is a duplicate question. Every video I've tried to learn from only solidifies the faces (ex: https://www.youtube.com/watch?v=UcBtvpwmcuQ) as opposed to an even fill throughout the mesh.
Basically, I am modeling for 3D printing. The objects I am trying to print are small enough to where they should and need to be solid. I was working on a token/disc and couldn't accomplish that so I went back to the drawing board with a basic cube to make a dice. When I apply the solidify modifier to the cube, I put it right on the threshold to where the next increment will break the visible/outer surface. I assume this means it is completely solid. However when I slice it in chitubox the layers are showing that the object is not completely solid. I feel that I've tried all settings, complex and simple versions of the solidify modifier. I am still getting incorrect results. Picture of a layer in chitubox and picture of another cube with the same modifier applied (scaling might be slightly different, I haven't yet figured out a way to view parameters of applied modifiers again once they've been applied). Again, if you feel this is a duplicate, pointing me to a forum that is attempting to accomplish the same thing is extremely appreciated. I have yet to find a correct source to learn a way to apply this feature in a way that accomplishes my goal. Thank you to any helpful replies in advance.
Edit: I've worked out that at least in this case it has something to do with the beveled edges. A regular cube mesh solidifies fine. Am I missing a boolean modifier somewhere? The token/disc I assume is having the same issue due to the geometry of the faces. I would attach a picture of that however I'm so deep into that project that I've forgotten what I've applied, in what order, etc.

