TT steps are to high sometimes.

My mother uses a folding aluminum step that sits below her 3rd step. It works well if the ground is completely level, but most times the ground isn't completely level, and it's an ankle sprain waiting to happen. If it's wet grass below it slips around, it wobbles when the ground is uneven, and even though the base is wider than the top, it still wiggles if you don't step in the middle of it.

If your husband makes one, make it bigger than you think you need. You want it to be as stable as possible. Since he's a carpenter, I'm sure he can make a decent step.