I have built quick doors before by just making a face frame that can be assembled with pocket screws. Just run the styles and rails (outside frame pieces) through a table saw on edge to carve out a 1/4" slot for some cheepo 1/4" plywood panel. Assemble the outside frames around that 1/4" plywood, screw the styles and rails together with the pocket screws. Use automotive bondo to fill all of the holes. Sand that smooth, prime, and paint. Another more simple option is to nail the 1/4" ply on the back side of the framework. Then, you don't need to cut out the grove for the plywood to sit in. That's more simple, but will look a little less professional on the back side.
A pocket screw jig is an awesome addition to a DIY kit. They can be relatively cheap and I use mine almost every day. They're definitely cheeper than what you would spend on a router, bits, and table. You might be able to buy one at the local hardware store but Rockler woodworking is sure to have them. They're on Colorado south of Denver. You'd be best to buy a small kit with jig, driver, and clamp. Don't forget the screws.
Just an idea. Works well for quick and cheep painted doors.
I can post up pics if you're not following what I'm suggesting.
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