I’m sloooooowwwly making interior panel doors for my house. Also paint grade. I’m using knotty old Douglas fir from the home despot and 1/2" plywood for the panels. I use plaster to fill the knots and imperfections. I have a few that have been through a full seasonal change and haven’t had any issues with them. I’m putting 2" long tenons on the rails and cutting a single 2" deep x 1/2" wide mortise down the length of the stiles. It makes construction easy.

It’s very important to clamp the door to a flat surface with cauls. I use my table saw for that. It’s almost long enough and the fence rails make for a sturdy platform.

Since I’m using this crap lumber, which is not thoroughly dried, cutting the mortises opens up the inside and allows it to start drying out. Do not wait to assemble or you’ll find that your mortises are suddenly a different width. LOL

Losing fingers since 1969