With the use of a sewing machine and other materials, making a homemade mattress is easy.
Sew the two flat sheets together on three sides, inside out, using a 1-inch seam. Repeat the process a quarter-inch away from the first seam. This will add stability. Turn the mattress sheet cover right side out where the seams are on the inside.
Decide if you wish to stuff your mattress with down feathers, shredded, flat, or egg carton-shaped fiber foam or with memory foam or other materials. Ripped-up clothing can be used as stuffing if desired. If using flat or other foam sheets, cut the foam a quarter-inch smaller than the size of the sewn-together mattress sleeve sheets.
Begin stuffing your mattress cover. For foam sheets, roll up the covers much as you would put on a sock and start at one end of the foam and work the cover up to the opposite end. For shredded foam or down feathers, stuff the material into the cover until full.
Pin or hand-stitch the end of the mattress cover together. Once you have a straight seam, sew the ends together using the sewing machine, attempting to keep the one-inch seam margins. Sew a second seam close to the first line of stitching to ensure the seams do not rip out.
Loose fiberfill, down or old clothing may shift as the mattress is used. Simply fluff the mattress regularly to keep the stuffing distributed evenly throughout the mattress.