Germinated seed and put it in the rockwool hole. ...

Always leave a gap between the bottom of the netpot / rockwool / cube so that the roots do not drown , if they are submerged in the solution you risk getting root rot ,and oxygen deficiency, personally I use root it cubes touching the bottom of my netpot filled with pebbles , try and make the distance to the solution as short as possible to let the roots get there quickly , the faster the roots get into solution the quicker the plant grows . I found that rock wool cubes stayed too wet for me , that’s why I use root it cubes , they are more like sponges , if you put the seed in the rock wool and cover it you run the risk that the plant cannot get out , I personally germinate in the cube then transfer into the pot . Germination needs three things , darkness’s , warmth and moisture . Good luck 👍