There are things called flanged threaded inserts that are like pop rivets that have an internal threaded hole. You screw a mandrel the right size onto the tool, like a big pair of pliers then the insert on to this Close the handles and this squeezes the insert onto the material. remove the tool and you have a threaded hole. The downside is that you need the tool and the right size insert plus there will be a part of the insert remaining on the top of the material. https://www.sealey.co.uk/product/5637203453/threaded-insert-rivet-nut-m8-splined-pack-of-50