Hey mates, np Im here to help.
I usually go from seed/cutting to rockwool cube (relatively small) into final pot. I dont like transplanting 6L->10L , etc. as it is quite messy with coco and you often break up the root system while doing it, hence why I usually always go for the biggest pot I can from the start. I have also done seed directly into final pot (3 or 6L) but you will have to be careful when watering as to not to disturb the intial small seedling. (If you dont have anything that disperses a gentle jet, get any water bottle and make a few holes in the cap)
However, if you really do need to transplant coco -> coco, I would recommend you wait until the coco dries up and you can see gaps on the sides/corners between coco and pot, in that case slowly reverse the pot upside down, with ur palm spread around the base of the plant/coco, with plant stem going between ur fingers, tap it gently to shake off the pot, remove the pot gently. Some ppl will run a knife around the edge between coco/pot before doing this, thought Ive never needed to. Once done, use the free hand to hold the bottom of the coco gently (too much force will break the cake). -Slowly- turn the plant upright again with ur hands trying to secure the coco and keep it from breaking apart. A helper would often be handy when doing this, and obviously the better rooted your plant the more your coco will have some inherent integrity as to not break apart when trying to transplant.
Goodluck