Leaving snow and ice under structure

I'm generating flying island as a structure in a snow biome. When it generates it leaves uncovered ground (screenshot 1) or unfrozen water (screenshot 2) under it.
I understand that this happens because my structure generates earlier than minecraft:freeze_top_layer feature happens. That feature is used on TOP_LAYER_MODIFICATION (last) generation step. And structures always generate before features if they are on the same step. Is there a way to make structure generate later than that feature without modifying biome files?
Or any other way of freezing top layer under structure will work too