Just My Size Closet

Before anything, decide how you'll handle the closet's existing baseboard trim — the simplest answer is to set the unit in front of it. Then build the center divider assembly with 3/4" pocket holes and 1-1/4" screws (or 2" screws and glue). Skip nails; with no back or face frame there's nothing else holding this together.

If you're using pins for the adjustable shelves, drill those holes now while the boards are flat and reachable — doing it after assembly is a reach-in nuisance. Then attach the two sides to the divider assembly, keeping everything square.

Fasten the top across the carcass, then the 1x3 footer at the bottom to tie the base together and give it a clean toe. Check the box is square across the diagonals before the glue sets.

Set the unit in the closet, level and plumb, and fasten it to the wall studs. For the rod, screw 1x4 cleats into the studs on the wall side and hang the rod bracket off those and the side of the unit, so a loaded rod pulls on framing, not just plywood. Add adjustable shelves on the pins and any extra shelving above the rod to fit.