If you have a flush stoma you need to use a convex flange of some sort. You can buy the convex inserts and use them with whatever flange of your choice, or you can buy the pre-cut convex flanges (which are a little deeper convexity). Having a good seal around your stoma is very important, that's why I used the Eakin Seals. They don't wear away as quickly as the paste and actually help heal the area. The paste also has alcohol so burns sometimes.
A convex flange will push the skin around your stoma back, helping the stoma to protrude into the flange. This should help prevent leaking. My stoma was so bad that I used the Eakin Seals, actually overlapped the edge of my stoma a little, then used the pre-cut flange on top of that which fit the stoma. It made my Eakin put a little ledge around the stoma.
You don't mention why you had to have the surgery, could you have ongoing disease? I have CD and the disease actually made my intestines shorter, so they pulled on the stoma from the inside creating an inverse convex stoma.
This is something you may want to talk to your surgeon and/or GI about. You do not want to battle leakage like this forever, you will have to have revision eventually. I put mine off until the disease was bad enough for surgery again, but had to change my appliance every 24 hours for years. That can get very expensive.
Good luck, let us know what happens.
49 years old, CD since I was a child.
Six resection surgeries, permanent ostomy, adverse reactions to Remicade, finally off of Prednisone, hoping for a long remission from this last surgery.