This is how I cut down cardboard egg cartons for lockdown. I did the holes in the bottom of each spot and used the trimmed down top of the carton as a riser placed underneath. I don't know if this is the best way, its just what I did. I've used egg cartons in one way or another every time. Supposedly every time a hatched chick is scrambling around in there, bumping and moving eggs around (if they are on their side) then the chicks in eggs have to reposition and it might take those knocked about longer etc. Who knows! I just use the egg carton method because it's nice! It makes for great viewing of the process and easy to keep track of pips and such. And if one did happen to have a smallish air cell my logic says it has a better chance upright. But hens do it ALL the time laying them down. So......