Cut the tenon shoulders on each rail using a crosscut blade and a sled. Clamp a stop to the sled

to establish the length. Make four passes, one for each face.

 

 I used a crosscut blade and sled to cut the shoulders of my tenons. All of the tenons on the base components are sized identically to make construction easier. Cut the shoulders in two setups. On the sled set up a stop so that the length of the tenon is one inch. Set the  crosscut blade to the depth of the tenon's SIDE cheek, 3/4 inch. Then cut the shoulders of the SIDE cheeks on opposite faces of each part being tenoned. Reset the blade height to 1/2 inch and cut TOP and BOTTOM ( FRONT and BACK on the verticle dividers) shoulders of the tenons on the remaining two faces of the stock. I then changed blades and installed a dado set, to waste out material and create the tenon's four faces. I used a miter guage with a temporary fence and the T-square fence to reestablish the tenon length, Repeat the two step operation used in cutting the tenon shoulders. Cut the tenon cheeks with the dado set at one height, making a series of passes over the blade to form the cheeks, then reset the blade height and cut the remaining two cheeks of each tenon. Clearly mark the faces of all stock. I went to trouble of setting all the components being tenoned with the same face up or down, so I would not get confused and cut a tenon to the wrong depth.