Install benderboard edging first, then put down landscape fabric (available at nurseries) to prevent weeds. Secure fabric edges under the benderboard edging.
Pour a 2-inch-thick layer of sand over the landscape fabric, raking it smooth. (In rainy areas, put down a 2-inch gravel layer first.)
As you rake, moisten the sand with a fine spray from the hose.
Firm the sand. Using a drum roller or a hand tamper, pass over the moist sand several times to pack it down.
Add steppingstones, then wiggle them in so they're firmly embedded.
To finish, fill cracks between stones with gravel, or ― to hold flagstones more firmly ― use something smaller like decomposed granite.