Stair Baluster Play Vanity

Assemble the base frame from the 1x4 rails. Before you fasten anything permanently, dry-fit your actual balusters into the leg openings — if the plan's dimensions don't match your balusters' diameter, adjust the opening now rather than fighting it later.

Attach the top to the base. Finish nails and glue driven from the top is the simplest approach; 3/4" pocket holes from the underside also work well.

Set the baluster legs inside the base frame and nail or screw them to the base.

Build the drawer box to fit both your slides and the base opening — as a rule of thumb this is about 1" less than the opening's overall width (1/2" clearance per side is standard for most slides), but confirm against your actual slide hardware before cutting.

Mount the drawer slides to the base and drawer box per the hardware's instructions.

Trim out the plywood top edge with moulding for a more finished look — this also hides the plywood's raw edge.

Attach the drawer face to the drawer box, leaving an even 1/8" gap on each side against the opening.

Support the mirror as needed for its size and weight — the corbels may need to sit at an angle rather than square, especially with a taller mirror. Dry-fit everything before committing any screws.