there's still a rhizome...you can either tie it to a rock, driftwood, or try to just weight it down with a rock. just don't bury the rhizome under the gravel or you'll kill the fern.
The anubias are planted the same way...don't bury the thick rhizome, just the roots coming off it.
On the crypts, you can plant these like a normal terrestrial plant, but the 'crown' where the leaves all sprout...that should be above the gravel and not buried. So you should have a little bit of white above the gravel, before it splits into leaves.
Also, expect the cryptes to melt...several leaves will disintegrate. This is normal. Cryptes don't like to be moved or bothered, and they melt when they are disturbed. After a couple weeks, it'll start putting up new leaves. If you have any root tabs, put one under each crypt to help reduce melting.
