I have been told and seen two different methods. Industrial Strength Velcro......and some sort of snap studs attacked to the inside of the armor and to the flack jacket....opinions or other options ?
I used chicago screw posts epoxied to my armor plates. The rounded screw heads go through grommets in my vest and screw into the posts:
I used snaps on the flightsuit to attach the codpiece and kidney plate. The male snap sides were punched into some plastic card and abs-cemented onto the plastic:
I would not recommend hot glue. If you are going to wear this and troop in it, your body heat alone will be enough to make it fail and if you troop in an area that is hot, like where I live, it is just about guaranteed to fail in the heat. I like to use CA glue (super glue) with an accelerator to quick set it.
This post by Bobamaker has a good technique and photos. As he mentions, you can use cardboard [or even posterboard from the grocery store or a for sale sign from hardware store] to mark the spots on your armor's inward side and on your vest.
You can use that method for magnets, snaps, screws, Chicago screws, etc.
I have had great success with JB Weld to hold the screw posts to the armour. As for the snaps, I punched a hole in a 2"x2" card of ABS and punched my snap through that. It was glued on with plumber's ABS solvent glue to my ABS/Boltaron armour.
It is so far! I did use a little sandpaper to rough up the inside surface of the armour and ground down the polished surface of the screw posts before using the JB Weld for better adhesion. As for the ABS tabs, I didn't do any special surface prep. Just the solvent glue was all. They are still holding!