Decide what size you want your chaise to be, given the space you have in mind for it. To allow an average-sized adult to lounge comfortably, it will need to be approximately 30 inches wide by 48 inches long.
Construct the base for the chaise. Cut two pieces of 2-inch-by-4-inch timber to the required length and one piece to the required width. The other end of the rectangle will be both the base and arm of the chaise. Cut a piece of 2-inch-by-12-inch to the required width. Butt these pieces together to form a rectangle and nail together with a nail gun.
Cut a 4-inch-by-4-inch piece of board to make the legs for your chaise. Decide how far off the ground you want the chaise to be and cut each leg to that length. Attach a leg to each of the interior angles of your rectangular frame with the nail gun.
Cut 1-inch-by-3-inch struts to the width of the chaise. Nail these along the length of the chaise to form the seat. The structure of your chaise is now complete.
Fill any nail holes with wood filler and sand any rough edges from your chaise frame. Paint, stain or varnish the frame in a color that coordinates with other furnishings in the room.
Cut a piece of 5-inch, high-density upholstery foam to the size of your chaise to form the seat cushion. Cover the cushion in a fabric of your choice that coordinates with other fabrics in the room. The easiest way to cover the foam block is to wrap it as if it were a gift, folding fabric under the cushion and sewing seams together on the underside of the cushion.
Use two or three throw pillows in coordinating fabrics to lean against the arm of the chaise.