wrap outside of rockwool in foil leave bottom and top open you want your roots to come out the bottom before you move to dwc, try putting some rinsed leca down on your tray under the rockwool 1/2" or so.
Be patient if unless you have a drip ring, You are better off trying to get as many roots going prior to putting it in your basket so your plant is getting roots into the water faster without having to raise water lvl too much ;).
Are you planning on using RO water have you tested your water yet?