How Can I Build a Bigger Butt?

Answer:

That's an excellent question and, to be honest, many of the most effective glute building exercises also work the legs strongly as well, e.g. squats, lunges, etc. There are definitely ways to minimize the effects of the exercises on the legs and focus more on the glutes.

For that, you can use the same tips that I would give to someone who feels all the exercises in the thighs more. Have a look at the following article:

Tips, Tricks and Techniques For Building Larger, Firmer, Rounder Glutes

When the focus is on the glutes, and they're getting more of the work, more of the recovery energy is going to the glutes and won't be going as much to other bodyparts, so your gains will be more focused on the glutes.