Felted soap is fun to make, and also makes a very nice gift. It is inexpensive, handmade, and doesn't take much time. I often just tie a pretty piece of handspun yarn around the soap and attach a tag to the yarn.
You can hand card a small amount of fiber, about a big hand full. You can also use a batt, or even strips of roving. Mostly you will just need to try and keep the wool at an even thickness, and avoid any holes or thin spots. I blend several colors lightly with the hand cards, adding bits of color here and there. I try to use medium colors so that it will not look dingy after a few uses.
Wrap your batt around the soap carefully, leaving plenty of overlap at the ends and where the edges meet. An inch or so is enough, a little more or less will work fine. Break off the extra fiber, or go ahead and wrap it around the soap twice. This will just give you a thicker felted covering.
Fill a sink full of water as hot as you can bear. Some people may wear gloves, but for me they seem to stick to the wool and make it harder. The water just needs to be hot, not scalding, so bare hands should be fine, just make sure the water isn't going to burn you.
Hold the soap in both hands, covering as much area as possible to hold the wool in place, and gently submerge it in the water. Once it is nice and wet. squeeze it very gently with your hands to kind of mash it to the soap.
Now you can begin gently rubbing the soap lightly with your fingers and begin felting. Rub the whole bar surface until it is all lightly felted. Once it begins to hold together, you can rub more vigorously. Be sure and rub the edges and ends of the bar of soap as well. Don't worry if nubs form, you can trim them off later.
Now all there is to do, is keep rubbing, adding water, and rubbing more. This part of the process takes around 10 minutes or so. Be sure and rub all the edges and ends of the soap well, but don't worry if they are uneven.
Once your soap is pretty well felted, you can trim any lumps that have formed. Be sure and not trim so close that you make a hole. Once the nub is trimmed off, you can usually rub it down into a nice flat felt covering.
You can now shock your soap several times by rinsing in cold water and rubbing alternately in hot water. This will just shrink the felt up a little tighter.
Now squeeze all the extra water out and wrap in a clean towel. Squeeze the rest of the water out, and your soap is done. It will dry very quickly, and be ready to give to someone special.