So I picked up this young larch from the garden center today and got it into a makeshift grow box. I opend up the rootball a bit, and washed out a good portion of the field soil, but didn't trim. My instinct tells me to wait until next winter to trunk chop, but what are your thoughts.

it already has buds opening.

What do you consider a trunk chop? Note that larch is VERY resistent to creating new buds, and mght die before doing so.

I think you can do with a lot more trunk on there, so leaving it a year is fine.

I mean cutting it back to a new leader... not a chop like with a tree that back-buds. there are a few potential spots.