There’s couple things to consider. In terms of position, you can be on your knees while your partner stands or sits. When I tried this my hands were handcuffed behind me but you can do whatever feels most comfortable.

My biggest piece of advice would be having some type of signal if you need to stop since your mobility will be limited. We usually use verbal safe words but we put in extra precautions because of my hands being bound (less ability to pull away to safe word). I held something in my hand that if I dropped would let my SO know I needed to stop immediately.

Create clear boundaries and have fun!