Simple layering is done by bending a branch to the ground and burying a portion of it. Leeave the tip of the stem uncovered. A peg or stick can be used to hold the stem in place and ensure that it remains in the soil.
Layering is usually done in early spring while plants are still dormant or in late summer on anny plant that has not become woody. Plants with flexible branches are particularly suited to this method.
A light soil increases rooting success, as will wounding buried section. Treatment with rooting hormone is helpful.
I have tried this method with clematis and it works well.