On the glass all you can do is collect the larva after they hatch.
For the next time, after the current clutch hatched, place a ceramic tile, flowerpot (or just a shard) or a smooth rock in front of the current location and hope the clowns will lay their next eggs on that.
I found the best is to offer the clowns a ceramic flowerpot as anemone replacement. Then they will lay their eggs to the inside of that.