First off get your tools, you'll need small amounts of colors of your choice of merino roving or other breeds of roving wool. Fleece may work but will probably take longer to felt. You'll need you're felting needles and your felting pad. I use a hard sponge type pad with felt on it to help prolong the life of the pad as it does break up and it helps to protect the wool from getting contaminated as well by the felting pad.
Next hold your felting needle like you do your pen but hold gently
Start laying out the wool in the general shape and start stabbing by going up and down in the same motion so you don't break your needle. You must go in and out at the same direction any bending will bend the needle and therefor will break it.
Start shaping the wool it will look a little odd at first bit it will come together in the end
move the wool gently into the shape continuing gently poking it to help tidy
the fibers together
shaping should continue and if you haven't made a long enough shape just add to the
other side so it is even.
Add color by pulling a little out and laying it on the heart shape, feel the inside as you poke so you can tell the wool is shrinking in the right way.
Keep stabbing wool until it looks like this
Add a small blob of any color of your choice
Peel off gently from pad
Tidy ends now be careful of your fingers at this stage go around the heart and pinch, squish and poke into shape until you are happy.
Here is your abstract heart without a cookie cutter!