First, I cut all the parts out of pine.
I connected the pieces of the sides of the cabinets using dowel pins, and glued and clamped them.
I pre-drilled a gazillion holes. (Yes, precisely a gazillion.)
I connected the back pieces to one side piece with screws,
and screwed in the shelves. Each shelf is made with two pieces of pine glued together with biscuits. Adding the front piece to each shelf ensured the front edge of each shelf would not be end grain.
Below is the cabinet with the other side and the top connected. The top is made with two pieces of wood glued together with biscuits.
It took 74 pegs to fill all the screw holes. Okay, not exactly a gazillion. Even though I think one side and the back will not be visible (I plan to attach the cabinet in the corner up off the floor rather than use it as a freestanding unit), I figured I'd finish all the holes so it could have other potential future uses as well.
After I'd trimmed all the pegs and sanded the whole cabinet, I made sure these baskets will fit in the cabinet the way I envisioned.