Measure the mattress size
Decide the bed height and frame dimensions
Gather materials such as lumber, screws, brackets, wood glue, sandpaper, and finish
Cut the side rails, end rails, center supports, and leg pieces to size
Sand all cut edges and surfaces
Assemble the outer frame with screws and wood glue
Add center support beams for mattress stability
Attach legs or a base structure to support the frame
Install slats or a solid platform surface across the frame
Secure all joints and check for wobbling
Fill holes and sand again if needed
Apply stain, paint, or sealant
Let the finish dry completely
Place the mattress on the platform bed