The point is to give the work to the glutes and not hand it to the lower back. If the lower back is what aches after a set, the angle or the load is already wrong.
Three days a week, with a rest day between. Rest 90 seconds between sets.
- Glute bridge. 3×8. Chin slightly tucked. The lower back does not arch at the top.
- Romanian deadlift with a light dumbbell. 3×6. Keep the back long, not rounded. Stop as soon as the lower back wants to fold.
- Step-up onto a low box. 3×6 each leg. Push through the heel of the foot on the box.
If the lower back takes a rep, drop the load and shorten the range. Do not push through that ache.