Rip 12-inch hardboard siding into a 6-inch width; ask the lumber yard employees to do that for you.
Position the hardboard along the intended walkway area; it flexes somewhat, if you want a curved walk. Pound stakes into the soil on the outside of the form every few feet and attach the flexed board to the spikes with 1-1/2-inch drywall screws. Do this for both sides of the walkway.
Mark the inside of the area with spray paint. Remove the forms.
Dig out the area to a depth of 6 inches, making the dug area 3 inches wider than the painted area. Replace the forms.
Tamp down the soil in the bottom of the dug-out area with a mechanical tamper.
Spread 4 inches of gravel along the entire walkway area and use a rake to smooth the gravel down.
Unroll wire mesh along the entire length of the walkway, cutting it to the width of the walkway with wire cutters.
Pour the concrete into the walkway area and spread it with a rubber trowel.
Run a 2-by-4 along the top of the walkway to screed the concrete and make it flat. Allow the concrete to dry until water appears on top. Smooth out the surface with a bull float, lifting the float after each pass.
Smooth fine spots on the walkway with a magnesium float.
Run an edger between the concrete and the forms to keep the concrete from sticking.
Run a broom over the surface of the concrete to create texture.
Cover the concrete with 4-millimeter plastic for three days to keep it from drying too fast. Remove the plastic sheeting and forms after three days.