The way that I do it is to let my seedlings germinate in some rapid starter cubes. I keep them watered and in a relatively high humidity area using a mister bottle. I do this until they are of a good size, and have a few roots growing out of the cube.
At that point they look similar to this:
Once they have reached the stage of growth where the roots are coming out of the sides of the cubes, I take my netpot and layer a single layer of hydroton onto it. I then carefully place my cube onto the hydroton, and start adding hydroton around the cube so that it will be supported. When I'm done with this, I usually have a single layer of hydroton on top of the cube.
Then I transplant it into my DWC system, and make sure that the water doesn't touch the cube, but that there is a gap of air where the water can bubble onto the cube.
I don't know how well I explained it, but I can draw a diagram if needed.