Cooker legs usually screw into the cooker from below - into robust threaded holes - they're adjustable for levelling the cooker. They may well pass through a crap metal plate but they'll go into a strongly mounted hole.
It's a puzzle how they became detached in the first place - somebody has been screwing around (anticlockwise) with your cooker legs.
Very creative the 28 mm worktop - but it will present a tacky image to visitors.
Good Luck...
July 2016