Step 2: Acquire a large block of foam
The shape we are going to form out of this is quite complex and I found it difficult to visualise. Therefore I found that sanding down a large shape was much easier than trying to build the completed shape out of measured strips, however more time consuming.
At one end of the block, mark the centre and draw a circle 140 mm radius. On the other end of the block, mark out a rectangle the same width as the block and 165mm high, again making sure that it is centred.
Now begin sanding. I used a large metal file, however low grit sandpaper would do the trick. Whilst sanding, you need to keep in mind that the middle band of your shape is to remain virtually untouched. This allows the two sides to merge smoothly together, as pictured.
Whilst sanding the rectangular side, it will be the foam above and below the shape which you remove, whereas at the circular end it will be the width of the block that will be reduced, and any corners rounded off.
In the final stages, use a high grit sandpaper to smooth the shape.