Porcelain tiles (about $1-2 at Home depot) laminated together offer better single shot protection than Kevlar. You-tube has videos of a stack of porcelain about an inch thick defeating .308, .223 (check you-tube videos for "homemade body armor")
Porcelain is considered harder and stronger than ceramic tile.
Ive seen them just wrapped in duct tape, but a proper epoxy between layers and a few layers of nylon or Kevlar over it all for spall protection....well thats some decent DIY armor.
Keep in mind, the highest rated ceramic rifle plates available (level IV) are about .75 inches thick, and weigh about 7 pounds each. 7 pounds of porcelain tile stops a HECK OF A LOT of rifle bullet!
Remember, its not just the material you use, its the order you put them in. A hard outer surface can be designed to fragment or deform projectiles to lessen their penetration into further layers. Hard, layered to soft, layered to hard, etc. Think of it like rebar in concrete- support brittle with flexible
A tile cutter can be used to clip the corners for a "shooters cut" or to help your homemade plate fit in standard plate carriers.