It should work depending on what time of year you layer it. Just don't try and detach it and move it for two years. Use the same procedure for layering in the soil. The attached photo shows two layerings though I know it's not easy to distinguish one from the other.
Remove some of the dried leaves, one by one, but you can leave some that will gradually deteriorate and form a protective base for the clematis to help keep the roots cool and moist.
Anna is right. A drink of Epsom salts a few times a year will encourage new stems to emerge.
I pruned mine after bloom and it does well, providing blooms most of the summer.
