First read Clownfishes by Joyce Wilkerson It walks you through step by step.I have a copy you can borrow
You don't have to remove the rock.You can let them hatch in the main tank and then collect the larvae.Do you know when they will hatch?
On the night you think they are going to hatch wait for the tank lights to go out and turn off all pumps. Tape a small LED light in an upper corner of the tank and then wait they usually hatch 30min-2 hours after the lights go out.They go to the light and you can scoop them out.
Now feeding,First food is rotifers and then Otohime
You need alot of rotifers for a batch of clowns so you need to get a culture going.I used 5 gallon buckets for my cultures.I fed the rotifers Instant algae Nanno 3600
Feeding technique,First I feed the rotifers like a hour before the larvae to fill their guts. Then siphon the rotifers through a 53 micron seive and feed to the larvae.