First of all draw a line segment that is about 2 cm long between two points P0 and P1. At the one of the outer points, draw another line that is at an angle of 90 degrees from the first line segment. This will cause the new line segment to stand straight on the first segment. Draw another line segment between the not used endpoint of the new line segment, let's call it P2, and the not used endpoint of the first line segment. This will create a triangle. Now on the P2 endpoint, draw another line segment that is again at 90 degrees angle. Repeat the previous steps and you will have created a root spiral.