Folks pretty much covered striking cuttings, except hardwood cuttings will take root both out and indoors. For us it seems to be more a matter of consistent heat, drainage & moisture… and not too much of heat and moisture.
Size. Last year was experimenting with how large of a hardwood cutting would push roots as small ones didn’t seem to be a challenge. So a small chunk likely 5-7yoa 2x2” Kazan (didn’t have any larger) was pruned and immediately struck in one of the large pots by the fountain… and promptly forgot about it. The pots stayed out all winter and come April finally looked down at the pot to see the Kazan had survived with a decent body of roots.
Outdoors. When taking cuttings we often strike a bunch of extras in large pots on the ground in the splash zone of a fountain. Or simply strike these in the same pot as the older developing pre bonsai Satsuki the cuttings came from (saves a label if one is short on time). Another method used is to take seedling mix (40:60 peat

erlite) and strike 20ish cuttings with a little spacing in a 4” nursery pot destined later for designs requiring a bunch of stems. Use of a semi shade microclimate in the growing area is best.
Satsuki in the landscape. In Puget Sound the older Japanese nurseries always had Satsuki in inventory. Old fashioned large leaf large flowers were planted in the gardens of the Puget Sound Area by ARS folks back in the day 50ish years ago all around the Sound. These do grow pretty large. A newer group of ARS members has planted Satsuki that are more compact both in leaves and in flower size. However these planting are very rare nowadays as the older homes are torn down and 10 townhomes replace them.
Cheers
DSD sends