Cut the door stiles, or sides, equal to the height of the door and the rails, top and bottom, equal to the door width. Using a dado head in a table saw, adjust the height to a third of the thickness of the wood used for the stiles and rails.
Attach an auxiliary fence to the table saw, and feed a rail face down into the blades. Turn over, and feed rail into blades again.
Set dado head of table saw at 1/2 inch. Turn rail on its side, and run into blades. Turn over and repeat. You now have a "tenon cheek" on each end of the rail. Repeat with the other rail.
Drill a series of holes on the inside edge of each stile, 1/2 inch from the ends. Holes should be 1 1/4 inch deep and 5/16 inch in diameter. Clean out with chisel to form the mortise. With a 1/4-inch cutter in a router, cut grooves in the sides of each stile between the mortises. Repeat for inside edges of rails.
Section 3/4-inch wood stock to size for the door panel. To make a raised panel, set the table saw blade at a 15-degree angle and run against the auxiliary fence on edge. Repeat on all four edges. Then set the blade at 90 degrees, adjust blade height to depth of groove on the rails and stiles and run over blade on all four edges. Sand edges smooth.
Squeeze wood glue into the grooves and mortises on the stiles and rails. Set door panel into grooves, and assemble the rails and stiles with the tenons fitting inside the mortises on each piece around the door panel.
Hold together with clamps until glue dries. Sand the entire door smooth. Add handles and hinges in whatever style you choose.