One of the cheapest ways to build a twin platform bed frame is to use ash blocks. You will not have to buy expensive wood or metal or screws; you do not even need any tools, and because the material can be so cheap. Determine how many ash blocks you need based on the size of the twin platform bed frame you have. For a double bed you need four blocks, for a double bed you need five blocks, for a queen bed you need nine blocks, and for a king bed you need thirteen blocks.
Then for build simple twin platform bed frame, measure and cut your plywood board to match the size of your bed. You want to subtract an extra inch of length and an extra inch from the width, but to avoid raising your legs or feet on the side of the plywood board after you have made your mattress on top. Place four ash blocks on the floor to match the four corners of your bed. Put the blocks on their sides.
Place extra blocks on the floor if you have a mattress larger for twin platform bed frame. Place a block in the middle of the configuration if you have a double. Put your plywood board on the blocks and arrange the configuration of the blocks if needed. Place the mattress on top of the plywood board.