To begin start with wool roving. Tear in 3-4" chunks. Lay down in alternating directions. I placed my wool on a layer of bubble wrap inside a disposable paint tray liner available at your local home improvement store. You should also add a layer to create agitation such as wire mesh/tulle. Use a squirt of liquid dish detergent with warm water and mist/spray the wool. I folded the bubble wrap over the wool roving layers. Using a pool noodle roll over top of the wool. In the photo below I've used pipe insulation in place of a pool noodle.
This is the finished dry felted piece. The inspiration was an abstract landscape of a day at the beach.