Step 3: Hollow out the coconut.
Once you have the two halves separated, a good trick I read for loosening up the meat of the coconut for removal is to pop the bowl-half into the microwave. Two minutes should be sufficient; it will be quite hot when you take it out, so use caution, and give it a few minutes to cool down again before proceeding to the next step.
To remove the meat, the original tutorial I found suggested the use of a chisel, but I found that after microwaving, a spoon worked equally well. The way to accomplish this is to score across the diameter of the fruit with your box knife, creating pie slice-shaped sections. You can then wedge the tip of your spoon between these and the shell of the nut, and pry them loose in more or less whole chunks. Ideally, the membrane between the meat and the shell will come off with them, leaving the inside of the shell bare; it should have a rough texture and look like tightly-packed plant matter.