Cut three pieces of 16-inch-long boards from a piece of 1-by-8-inch oak lumber with a circular saw.
Apply glue to the sides of two pieces of board and clamp the glued sides together to form a 16-inch square.
Center the third board over the joint of the glued boards and secure the board to the glued board with 1 3/4-inch wood screws.
Flip the board over so the smaller board faces downward. Draw the largest circle possible on the board and then cut the circle out with a reciprocating saw.
Find the center of the circle and drill a hole large enough to fit a 1 ½-inch nylon rope through it. A hole saw is the perfect tool for this task.
Sand the edges of the wood with a sander and then paint or stain the wood. Wait for the paint or stain to dry before moving on. Use an exterior paint or stain. You can be as creative with this process as you like.
Drill a hole vertically through the thickest branch on the pine tree and insert an I-bolt through the branch. Secure the I-bolt to the branch with a washer and two bolts. You need a wrench set to secure the bolts.
Tie the nylon rope around a metal thimble and then use a secure hook to connect the thimble to the I-bolt.
Thread the nylon rope though the hole in the wooden seat and then tie two large knots in the rope below the seat.
Cut the excess rope off with a hacksaw.