The customary way to do this is to take your apron piece, rip off the top and bottom pieces, then glue them back together after cutting out the drawer area. This picture will help illustrate that:
|Cutting Mortises, note depth block|
I use a hollow chisel mortiser to cut my mortises. I started out years ago doing them all by hand the same way my junior high school students were taught. Then I graduated to getting a drill press, then a bench top mortiser, and now finally a dedicated hollow chisel mortiser. It's nice to know I have the ability to cut them by hand but this sure makes it easier. They still require some clean up work with chisels but all in all, this is the best method for me.
The apron will be 4 1/4" wide. For maximum strength I chose to stagger a 1 1/2" wide tenon in a full haunch that will be 1/2" deep. Lots of technical stuff here but the purpose of the full haunch is to prevent the aprons from twisting. I decided to stagger the tenons rather than having them meet inside the leg to increase the strength. The technique I use is illustrated by this picture; at the rear of the mortiser there is a black rod which is the depth stop. See the little block of reddish colored wood? It's 3/4" thick so when you cut the haunch, that is put onto the stop which limits the depth to 1/2". For cutting the full depth mortise, you remove the block and cut the full 1 1/4". Simple little trick but works quite well.
Well, the sun's coming up so that means I can make noise out in the shop. Glad to say our weather has cooled down considerably so working conditions are much improved!