A good leg day should be full of hinging. This hinge movement allows you to use your glutes and hamstrings without putting impact on your knees. There are several variations of this movement based on your experience level but I find this to be the most applicable at any level.
This movement can be done flat on the floor, as well as with your feet elevated. Begin this movement with your back flat on the floor and your hands beside you. Then squeeze your glutes to lift your hips of the ground. End the motion when you feel the hardest glute contraction or when your hips are in line with your legs and core. Also, try the single leg variation for a challenge and extra hamstring work.