Yes, stomas protrude out, and a convex with a belt is designed to assist it to do that for those with recessed and flush stomas.
If you eat something that the intestines have a hard time pushing out, like a banana eaten by itself, the stoma will appear to swell and protrude out. This is something to be avoided as it will mess up your seal and cause pancaking.
What I do now is use a lot of no-sting paste, 1/2" wide and thick on the skin first to ensure adhesion, then another bead on the wafer and married together, pushed gently down so the paste just appears around the edge of the wafer hole. Then pressed gently down a bit around the stoma to ensure skin bond.
This results in the paste forming a wall, and I hold this gently, laying down for a few hours until the paste hardens up some. This way, if the stoma protrudes, it's rubbing up along the sides of the paste wall and maintaining a seal.
I, of course, press the wafer flanges down and put a tiny bit of olive or coconut oil-based skin lotion on my scar tissue, cover it, and fill my belly button hole with toilet paper and thin cardboard before applying extra-large barrier strips all around well.
I normally would need an ostomy belt (I use the Coloplast four-hook belt and convex) but have been getting away with no belt for a while to see how it goes.
The stoma does protrude up and down according to output pressure. I have a near flush stoma, so at least some of it is up already, but I use a convex anyway as I have a belly fold.