Crafting weapons is a new mechanic that was introduced in season 6. You are now able to craft a stronger weapon by finding components around the map.

You will need a makeshift weapon and either some mechanical parts or some animal bones to craft either a mechanical weapon or a primal weapon.

Mechanical parts are found from destroying cars, buses, trucks, tool boxes and boats.

Animal bones are found by killing animals or destroying bones that are found around the map. If you are in a primal area the buildings and surrounding area will be decorated with bones.

When you have a weapon and enough components to craft you will see an icon above the weapon in your inventory notifying you. Just bring up the crafting menu and you will be able to select a weapon to craft. Crafting takes about 3 seconds so make sure you don't do this in the heat of battle.