Dig holes 2 feet deep and large enough in diameter to hold posts. Space them at regular intervals along your planned fence line.
Insert a post into one of the holes. Hold it in place while filling in the hole and tamp loose dirt down tight around it. Pour concrete in the base of the hole for extra stability first, if desired.
Wrap one end of a nautical manila rope around the end post in a round turn, a few inches from the top, with the working end of the rope going beneath the what's known as the standing end and then crossing up over it. Wrap it around the post once more, pulling the working end down through its own loop and tightening. This is known as a clove hitch. Tie a half-hitch with any slack remaining, looping it around the standing end and pulling it through.
Move to the next post with the working end of the rope and tie another clove hitch, leaving a little looseness between this post and the first one to give the rope fence the traditional sag. Tie a clove hitch on every post along the line, then finish with a clove hitch around the final post and a half hitch around the standing end to secure it.