I am making a rolling stand for my planer. It is made out of 2x4 material that I milled 4 square. 36lx32wx33h. The long (36") horizontal plane / portion will have the 2x4 on edge, with the the other 2x4 mortised in from the height side. Basically I am making two side frames and then want to put braces across for the width. Since I already have mortise on the side frames, I am having trouble figuring out what joint to connect the across braces with. I can't use another mortise since I already have those cut in those pieces and I can't use a dovetail as there wouldn't be enough meat left because of the mortise, what would be the proper way to make this 90? Obviously I could use some pocket holes, but I very much so dislike them and can use the joinery practice. So basically I am making a crate and can't figure out how to connect the three legs together. What is the traditional way without fasteners?
Thank you