Step 3: Boiling
Microwave the solution to boil off the water. It took me about 20 minutes on High. I did this in three 5-minute segments, followed by a series of 1-minute segments.
Keep boiling it down until you start to hear sizzling and popping sounds. It should still be a liquid, though. If you end up with a foul-smelling yellow lump, you've gone too far.
The resulting volume should be about 1/10 the original solution.
Note: The container will be very hot.