Joining mechanisms

A possible joint for the leg frame could be a diagonal finger joint, both pieces have lower sections which fit together on top of one an other, this is very sturdy.

 A second possibility would be the mortis and tenon joint, it can also be used on an angled joint and allows a rectangular piece to slot in nicely into an a-joining hole. 

A third possibility would be a screw joint where both pieces are firstly glued together to bond the surfaces and then screwed from the bottom hiding any joining parts.

This is what the bottom and side of leg frame will look like once assemble together with a joint, the angle for the legs to sit at is 45 degrees.