Dig the walkway out to the depth of the stones you are using, plus an extra inch. For example, if the stones are 2 inches high, then you will need to dig down 3 inches so the tops of the stones will be level with the rest of the ground.
Fill the path with 1 inch of sand and rake it out smooth.
Place a level on the walkway to make sure that the path is flat.
Place the flat stones down in the walkway to fill it. You can do this one of two ways. Either place large stepping stones down to make a foot path and fill in around them with smaller pieces of gravel, or set down many flat stones, fitting them in place like a jigsaw puzzle. Set the stones in place based on the option you choose.
For stepping stones, test the spacing by walking the path after you've placed them. Move the stones as needed to ensure a natural walk.
Spread smaller gravel around the stepping stones to fill in the entire path. If you have filled in the entire path with flat stones, spread sand over the surface so that it will work down in between the stones.