What Dennis said. My flange is PVC too, on a wood floor. I can’t remember how many of the layers I used. But It did seal good about 5 years ago, still sealed.
My first house had a leak around the seal with a wood floor. The wood was rotten. Had to replace the entire floor and go underneath in the crawl space to get good wood and a good anchor to seal. That house had so many engineering problems, I was glad to get rid of it.
The sewer didn't have the right fall to carry all the solids. It was too steep. The drain from the kitchen to the main sewer was orangeburg plastic pipe that collapsed and delaminated requiring a complete replacement. The sewer it connected to was 14' deep so it wasn't a shovel job. The main from the bathroom/toilet was clay tile that had roots getting into it all the time. Even treatments of copper sulfide didn't stop the root invasion, and so on.