I'm not a pro a dwc, I failed my first attempt with it. I can cancel out my mistakes to try to help. I would leave the water a little underneath the basket. the bubbles from the air stones should be able to keep the bottom of the net basket wet, so you can feed from the top until the roots hit the bottom of the basket and you should be good.The roots will eventually hit the solution and will be submerged in the solution, just make sure that there is plent of oxygenation for the roots to breath. have you checked the ppm of your solition?
the more experienced with dwc should be able to give you more info.
hope this can help.