Dig four holes to fit the four 10-foot tall posts. You will need to bury at least two feet of the posts into the ground and set them with concrete. Let the concrete set overnight and fill the holes with dirt.
Use the string to level off a straight line from each of the posts. (This step is optional, if you choose to use a level for step 3.)
Attach a one-foot by eight-foot board to the outside of two posts and repeat around the perimeter of the posts to build the frame to the floor.
Cut off two feet from the 4x4x10-foot post and lay it down in the center of the floor frame from front to back. If you choose, attach it to the front and back boards using screws. The top of the post should be set four-inches deep into each of the one-foot by eight-foot boards in the front and back.
Lay down the floor supports using seven two-inch by four-inch by eight-foot long boards. Leaving a one-foot gap in between each board, attach each board to both sides of the floor frame using screws.
Finish the floor by laying down and attaching the remaining eight one-foot by eight-foot boards from the front to the back of the floor frame with screws to the floor supports one by one. (Note: You'll need to work around the insides of the posts. You might need to make cuts to the boards.)
Cut 18 inches off of 36 of the 2x4x8-foot long boards. These boards will be used for the height of the wall frames.
Assemble the wall frames by screwing two eight-foot long boards on the top and bottom of two of the freshly cut 6 1/2-foot long boards. The outside perimeter of the frame should be eight-feet long and 6-feet, 10-inches high.
Add seven 6 1/2 foot long boards to the inside of the frame, leaving a one-foot gap in between each board.
Repeat Steps 8 and 9 until you have four wall frames. (Note: On the front frame, remember to leave a three-foot wide by six and a half-foot tall gap for the door).
Attach the wall frames to the floor of the cottage house and to each of the four posts.
Build the roof frame by constructing three triangles. Use a 12-foot board as the base and cut the ends at a 45 degree angles. Next cut both ends of the two 10-foot boards at 45 degree angles. Butt up all angles of the boards and attach using screws to create a triangle. For support, cut the 2x4s to fit from the base to the top of the triangle. (Note: the roof will have approximately 2 feet of overhang from the main structure.)
Attach the roof frame to the top of the cottage house.
Cut four 2 1/2-foot by 4-foot sections off of two of the four-foot by eight-foot boards. This will leave two three-foot sections as extra paneling and allow for you to work around a door frame.
Make cuts into the paneling for any window holes. These can later be dressed up with shudders or some form of plexi-glass to keep it shut but let light in.
Attach the four-foot high by eight-foot long panels to the exterior frames of the cottage house and roof. Attach the 2 1/2-foot by 4-foot sections around the door frame.
Cut exterior panels to fit the surface area of the eaves created from the triangle shape of the roof frame and attach these to the structure.
Attach sheetrock panels to the interior frame of the cottage house with wood screws. Sheetrock is typically four-feet high and can come in many variations of length. For an easy time, buy it in eight-feet lengths and cut it to meet your interior dimensions if necessary. For a finished look, tape the line between the two sheets of drywall, spread mud between the two sheets of drywall and paint over it.
This step is optional.