I always just cut plastic bottles in half and fill the bottom half with soil,soak the soil real wet and stick the clone in the soil after i have dipped it in cloning gel and then make a smallish cut on either side of the top half of the bottle and push the bottle back on the lower half of the bottle and the seal it back up with some cling film around the middle.
Breathe slowly into the bottle to fill it with co2 and oxygen and then put the lid back on.
Open the bottle once a day and breathe slowly and warmly into it once a day.
Always works for me.
I notice that you in rockwool so i guess you'd just do the same thing but you'd have to add your growing nutes/water into the rockwool in whatever amounts it says to on the bottle for clones.