They make inexpensive steps for excersise. My wife uses hers for getting on the inversion table. A google search for "exercise step" will turn up plenty of them. They start at about $5 and vary widely in price. You should be able to find one that is the height you want that isn't too expensive. I am a woodworker, but, when she wanted the exercise step I decided I couldn't build anything to compete with what was on the market given the adjustability and price of what was available.