Not sure whats considered 'Proper Technique' but I used rockwool for years and it seemed unnatural at first to use them but really turns out to be as simple as it looks...its everything else that sneaks up on ya.
*ANSWER*
Seems like you already know the answer to your own question
Take a smaller of the cube sizes (2" is the started as I remember) and just jab a little hole in it just like you would putting a seed in dirt. Soak the cube and your done. When she grows a few inches tall plug the starter cube into whatever desired sized larger cube the plants will end up staying in.
*Note...again im not sure what the standard instructions are for this whole process (just telling ya what worked for me for yrs) but you can put the seed into the starter cube then immediatly fit it to the final size cube and just conseder it done. Also if you ever decide to take cutting or even for use with seeds for that matter....Its recommended that you get the round 'Stater Plugs' for seeds or cuttings...I would say just stick with the 2" starters that come in the slab and are SQUARE instead of round (and cheaper when I used them). The round plugs are too loose and dont seem to snug into the hole of the larger cube. The square starters slip into the round larger cubes hole more snug and still have the edges no touching so your not smashing everything togeather. Thats about it. Hope this answered you question and im sorry if this dragged on. Simple version...
1. Take 2" Starter (Square) cube or (Round) plug and make a hole into it just like planting a seed in dirt.
2. Drop the seed facing the proper way into the hole and gently pinch top (I like crimping the top of the cube to kill all light and simulate dirt) DO NOT SMASH THE ENTIRE HOLE TOGEATHER.
3.Place in water or whatever solution or method you would normally use.
4.When seed sprouts take the 2" cube and plug it into the final size cube.
DONE.
AGAIN HOPE THIS HELPED AND ACTUALLY ANSWERED THE ? YOU HAD.
Take care and good luck.