Not experienced with this but many aquarist use a plant substrate like Eco—Complete. They then plant the plant and cover the rest of the Open soil with a inch or so of sand. You could also use only. Water collumn feeders like java fern or anubius.
Another option if you want to use soil plants than only putting plant gravel around the plants and then lightly covering it to blend it in but have it barely accessible could also work. This option could also work with regular gravel and root tabs.