Raising equipment levels to proper height

What are some good ways to raise gear levels to proper height and keep it in place (so it doesn't slide around while playing)?

Currently I am trying to find some ways to raise my gear so that it's all level and the knobs line up. My LPD8 sits quite a bit lower than my VCI-400 and also slides and rocks while I play it. I fixed the rocking problem by sliding a small post-it note pad underneath one of the rubber feet, but the sliding and height problems are still an issue.