2x4 Captain's Bed with Flip-Down Storage

Build two 2x4 frames from the rails and verticals with 2-1/2" to 3" self-tapping screws (a screw type that doesn't need pre-drilling saves real time here), or pocket holes set to 1-1/2". Square is critical — the drawer/flip-down faces need to fit inside these frame openings, and an out-of-square frame will show as an uneven gap once the panels are hung.

Build the headboard and footboard panels from plywood or stacked 1x boards, and screw them onto the ends of the two main frames with 2" screws and wood glue.

Attach hinges to mount the drawer faces to the frames as flip-down panels. Mount the handles higher on the face than dead-center — a centered handle gives poor leverage when you flip the panel open standing up.

Stain the 1x2 and 1x4 trim boards before attaching them (much easier than masking off assembled parts), then screw the 1x2s to the top of the bed with 2" screws and glue, overhanging 1/4" on the outside edges. Screw the 1x4 end trim to the ends the same way, matching the 1/4" overhang.

Lay in mattress slats spaced about 4" apart across the frame, resting on the slat trim, and screw down at the ends.