Homemade fabric face masks are not a substitute for professional-level protective equipment like N95 or N99 masks.

The best fabric for homemade masks is a tightly woven, 100% cotton fabric. Things like denim, bed sheets, and heavyweight shirts are all good options. Avoid knit fabrics (e.g. jersey T-shirts) because they create holes when they stretch, which the virus could get through.

Here are a couple videos

https://www.youtube.com/watch?v=zz0YpY6VqVU
Ready Set Sew: “As instructed in our YouTube video ‘The 15 Minute Mask’ you need the following: – (1) 15.5 X 8.5 inch strip of fabric (for the body of the mask) – (2) 4.5 X 2.5 inch strips of fabric (for the side casings for elastic or tie strings)”

https://www.youtube.com/watch?v=zB68tnsXQ2w
SEW DIY FABRIC FACE MASK: Cut 2 pieces of cotton fabric 9 x 8 inches, WxH (23 x 20 cm) • Cut 4 ties, 18 inches long each (46 cm) • Finished height (after pleating) should be 3 inches tall.