Sorry to hear about your issues. Been there. Done that. Got most of the wardrobe.
I got a permanent ileostomy 3+ years ago. It was a little rough at first. Once I found the right ostomy product and procedure, it got much better very fast.
I suggest getting samples from several companies, Coloplast, Hollister, Convatec, etc. All LOVE to send samples to prospective customers - free! All have good and bad points. Ask for CONVEX skin barriers. See what you like.
I have a very lovely, protruding stoma on very flat skin, but 3 months after surgery with few problems, I could NOT get a flat barrier to seal - just like you describe. Nothing I tried would work. To make it worse, we were in Nevada visiting our then 6-month-old grandson. The convex supplies I ordered 2 weeks before the trip got backordered. I was changing skin barriers almost daily, and FOUR times one day! I had to buy supplies out there, off the shelf, and still could not get convex skin barriers. My skin was RAW. WHAT A NIGHTMARE!
When I finally did get the convex barriers, the problems diminished significantly. I do still have occasional overnight blowouts. I have not had any other leak issues in 2 years.
Possible causes of leaks.
Wrong skin barrier. Try a convex barrier.
Use only "pure" soap. Liquid body wash, soaps with body lotions, skin softeners, etc do not wash off cleanly, and the residue will hurt adhesion.
Make sure the skin is very clean and very dry. A little water or stoma output, even if wiped off, destroys adhesion.
Warm the skin barrier to body temp to improve adhesion.
I found Adhesive Remover absolutely necessary for best adhesion. Before I used it regularly, I would occasionally get overnight blowouts from ballooning. This was usually a skin barrier failure. Since using Adhesive Remover every time, I have fewer blowouts, and they are now between the pouch and skin barrier - pouch replacement only!
Ballooning is my biggest issue. I found a product called OSTO-EZ-VENT by KEM Enterprises. This is a small plastic piece you stick to the pouch. Punch a hole in the center of it (I use a toothpick) and the gas can escape the pouch. I get them from my ostomy supplier. I may stick a toothpick in my pouch 3 or 4 times a night, but then I do not need to get up.
My appliance choice is Coloplast 2 piece Adhesive Connection Sensura Mio
My current procedure for ROUTINE changes is: For emergency, follow as closely as possible.
Do it first thing in the morning before you eat or drink anything. This is your best shot at a quiet stoma.
Remove the skin barrier, wipe the area clean with toilet paper, then CLEAN THE AREA WITH AN ADHESIVE REMOVER WIPE. Big ones are better.
Take a shower. Clean the area around the stoma several times with soap. I use Dial exclusively. DO NOT USE a soap with extra stuff like body lotion or cream. Dove or Camay are absolutely forbidden! The additives prevent tight contact. RINSE THOROUGHLY.
As soon as practical, fold a sheet of toilet paper in half, and wrap it around the stoma. ANY LEAKAGE FROM THE STOMA ONTO THE SKIN WILL DESTROY ADHESION! CHANGE THE PAPER AS NEEDED. I do this and all steps that follow in front of my sink. I have a small plastic tub by the sink for trash.
Dry around the stoma as best you can. I have a dozen cheap white washcloths dedicated to stoma care. Keeps me out of trouble with wife.
I then use a hairdryer to completely dry the skin around the stoma. It's useless on my head, but works well for this! Wet skin also inhibits adhesion.
I apply a liquid skin protective barrier. If needed, powder would go on now, then more liquid. ALLOW TO DRY.
I use a paste around the skin side of my barrier to stop leakage onto my skin around the stoma. I warm the skin barrier some with the hairdryer. I want it about body temperature. I now remove the toilet paper and QUICKLY place the barrier over the stoma. I try to not touch skin immediately, but rotate the barrier 90 deg each way to help distribute the paste.
My stoma is 1 inch, and I have a 1-inch white plastic pipe coupler which I place over the stoma and press the barrier in place. This applies nice even pressure near and around the stoma, helping the seal. I press RADIALLY - from the center out - to stick the barrier to the skin. For a two-piece system, The hose coupler also acts as a chimney to protect the landing area for the pouch from stoma output. MAKE SURE THE LANDING AREA HAS REMAINED CLEAN. CLEAN IF NEEDED. As quickly as possible, attach the pouch. If it is an adhesive contact, be very careful to press from the center out. If you press around the seal, you will often not get it absolutely smooth. This leaves a crease and a guaranteed leak.
CLOSE THE BOTTOM OF THE POUCH!! Been there. Forgot that.
Sit back and rest! You deserve it!