Attention to a New Body Part
The 'stoma' is near your waistline, and that defines your belt position on its ostomy device barrier.
The barrier connects the pouch to your body, and its dimensions change with brand, so proof comes from trying.
Aim for longest time between barrier changes with no leaks; e.g. you may be blessed if shower is more often than barrier change.
A few brands I've tried and show here: Hollister, Coloplast & ConvaTec.
Distance between pouch and stoma-cut-out affect how barrier fits your body & belt.
These pictures show n millimeters (mm) to remember.
Note this n is not the cut-out for stoma, but it does affect pouch usability.