Best way is to actually remove the rock the eggs are laid on. Obviously this can't always be done. But don't worry your clowns will be laying eggs like a couple of rabbits. About every 2-3 weeks if water conditions are right. If you really want to try your hand at raising the fry start a culture of rotifiers. Some people try w/o live food using cyclopeeze and ground up pelleted like new life spectrum. Some say blending up egg yokes with a bit if water works for the first few days. The trick is to keep the food suspended. The other trick is getting enough hatched fry to survive which is why removing them while they are still on the rock. You van tell when they are getting close to hatching by the color change and appearance of little silver eyes. Placing them into a small tank with nothing more than a sponge filter is fine, but once they hatch water quality needs to be monitored as the feedings will funk up the water.
Place a smaller piece of rock close to your clowns and anemone, somewhere easy enough to get to but a place the fish will feel safe with. If your fry hatches before you remove them they likely won't survive even the first day, but on the plus side its free very nutritional food for your other fish.