Plywood has a property that is very useful indeed for ensuring your pieces are rigid: it doesn’t have a preferred grain.
If you wanted an ‘L’-shaped section using solid wood, you would need to fashion two pieces and join them together. With any joint, there is inherent weakness: it’s weaker than if it were a single piece. With plywood of course, you can make this a single piece as it’s a sheet material.
This is a way I have used to enable one piece to ‘grab’ another without the use of a slot joint, or even a screw, nail, bolt or glue. Using a dovetail bit, a CNC router can mill a groove into plywood in which the gap at the surface is narrower than at the bottom of the groove.