There are many ways to assemble the frame. One of the best ways is to attach the legs to the rails by using dowels because of their strength.
Dowels provide strength and easier alignment and can be made of wood, metal or plastic.
Use pointed dowels with spirals to take out air pockets because they will set more glue and provide for maximum stability. The frame will be put together by using dowels. The centers of the dowel holes should be centered on the inside edges of the leg and rails. Drill dowel holes according to the plans, using a dowel jig or a horizontal boring machine. Apply the glue to the dowels, holes, and flat surfaces.