It's a porn genre.
If you avoid things like heavy boots, the risks are minimal especially as you will be starting gently. If it's just been a fantasy, the reality may well be too much and it may be worth having a bowl to hand just in case they want to throw up, but if it's something they've done before, they will know their limits and will guide you as to how much harder they want it.
There are several ways to do it:
1. Them standing, legs apart. You stand the around the distance of your leg away and kick appropriately, either by standing on one foot, other leg's thigh parallel to the ground and then use that leg for the kick, or do a 'I'm a football goalkeeper punting the ball away' action and use the whole leg. The latter is harder to control though.
You can tie their wrists to a door via 'over the top' straps which means a) you can spin this out and b) they're not going to hurt themselves collapsing on the floor.
2. Them kneeling in front of you while you're seated, knees apart. Again, get the distance right and it's easy.
If you tie their hands behind them here, there is a risk of them keeling over (but they've got less far to fall!) so you can just have them put their hands on top of their head when they're ready for the next strike.
You can also have them move on their knees forward to 'assume the position' each time. Have something on a hard floor - even dried pulses - and that'll hurt them too.
3. Have them on their hands and knees (or that, but lowing their head to the floor) facing away from you. It's easier with you seated, but you can also do it with you standing. Has the advantage that their penis doesn't get in the way and is probably the easiest way for a beginner to be on the giving end.
Again, you can have them move to the right position when they're ready for the next one.
Doubtless other positions exist...
Barefoot = less impact, but your toenails can complicate things. Light shoes can make it harder for you to judge the force of impact. They may well have a preference, and if so, will usually say.