Using a plastic bag to hone your skills in the sack
All you really need is a clean plastic bag, i.e from a loaf of bread or a carrier bag, and lots of oil or other lube and a couch/bed.
All you need to do is squirt the lube into the bag enough that you're satisfied but not so much that it will overflow. When you have the bag filled place the bag while holding the top between the mattress and base of your bed or between part of your couch so that the bag will be held in place with the top of the bag facing you. You now have a nice slippery hole for you to fuck. Experiment with more or less lube to your taste and exerting more or less pressure of the surface hold the bag in place.
I might not be putting it across very well but i assure you if feels amazing to fuck it. Just be careful when removing the bag, you don't want lube and cum pouring everywhere. Let me know in the comments or in private message if you've tried it and what you think of it, or if you can think of any improvements ect sharing is caring so pass around the pleasure.