@stilltortoise
I learnt long before the days of strapping my feet to pedals, although I’d struggle to explain the technique to anyone
With feet flat on pedals, try and ‘flick’ your feet backwards and up towards your bum. Maybe point your toes towards the ground a little if you fnd you’re slipping off. Concentrate on getting rear wheel off the ground first, then start practising hoisting the front wheel as well.
As learned back in 1981 on my Raleigh Jeep (with *very* curvy forks after multiple bunny hopping sessions…)