Answer: According to Michael Dirr's Manual of Woody Landscape Plants, buxus cuttings can be rooted successfully at any time of year, but that would include keeping them on a mist bench or in a poly-tent to maintain humidity.
In my experience a four to six inch tip cutting dipped in rooting hormone and plunged firmly into a sterile soilless potting mix will root successfully outdoors in the late spring to summer if kept evenly moist -- barely damp but not wet -- in a bright location but not in direct sun, and with a loose tent made from a clear plastic bag overtop to maintain humidity. I prefer to put one per deep four inch pot, but you could place several in one pot and transplant them to their own containers when rooted.
If you are determined to set them directly in the ground, you might be able to prepare the soil with extra sand and good compost and create a small hoop style poly tent over top of them to maintain the humidity.
The seeds will also germinate quite easily either sewn fresh or prechilled for several months to stratify.
You may find the following web page helpful, especially the diagrams and charts.
Plant Propagation by Stem Cuttings: An Introduction for the Home Gardener.
Good luck with your project!
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