As folks have said here, if you know where you want them and they are destined to be in the ground somewhere, plant and then graft next year is the easiest and may give you the best results.
That said, many here have used a hot callus pipe to graft bareroot rootstocks of persimmons and others. I used the MDC persimmon seedlings and built a pipe and had 65 out of 70 or so take and grow well. I basically bench grafted them, put them on the callus pipe for 3 weeks and then put them into tree pots. Of the ones that failed (all one variety), I’m pretty sure the scion wood I had for those wasn’t viable, so using the pipe can be quite effective.
Be aware that the seedlings are pretty small caliper, so if you are grafting them this year you don’t want big scions unless maybe if you are doing chip buds. When I’ve bought scion wood I’ve found some sellers can have some pretty big scions that really aren’t useful for smaller rootstock.