Single legged chair squats, or against a wall using a swiss ball, are a pretty hard challenge for most people (if you don’t cheat and lean your torso miles forward).
Single-legged glute bridges are also excellent, as are glute bridge walk-outs.
Walking lunges up and down the road with a heavy backpack (do them slowly, deep and with constant tension) are another good option.
3 hard sets of each of those and your legs will know about it.