You need to know what kind of surfboard you want. Pick a board that suits your style of surfing and the type of waves that will be surfed. You need to have an idea of the size, thickness, weight, number of fins, degree or amount and location of the rocker.
2. BUY A BLANK
There are about 10 general sizes of foam blanks that you buy. Pick one that is the closest in size to what your board will be. The blank is molded poyuveance foam....softer in the middle with a harder crust on the outside. Down the middle of the board is a piece of wood called the stringer that gives the board strength and "locks" in the rocker contour or shape.
You can either draw the pattern onto the blank or use a template to form the curves on the board. The pattern helps you determine how the desired dimensions will flow into or connect with each other. The pattern tells you how wide and how thick the board will be. It gives the overall shape to the board. A board can be made equal on both sides or made asymmetrically.
These are the "spin templates" that are used to make the different shapes on your board.
The planer gave the board a smooth surface.
Shaping the bottom contour in a tail.
A hand saw was used to cut the outline the board from the foam blank. It is pretty easy to cut. Then we would use an electric planer to smooth the surface of the blank.
The bottom was worked on next. The bottom was smoothed out and the rocker was shaped in. The outline shape was checked and corrected. We would get one side right then take a piece of paper and trace the shape and do the other side.
Then we would work on the top of the board, shaping the desired thickness into the blank.
Next we worked on the rails or outside edges. A good shaper can do all of this in about 3 hours. It's good to take a break and then come back and look at the shape one more time before adding the fiberglass.
This picture the side of the board and how smooth it is.