I made a rough sketch on the block; applied stop out varnish and crayon on the bits I wanted to stay solid. Left the varnish to dry for 48 hours, and then put the block in the caustic soda for two hours. Cleaning off the varnish was hard work -- it took about an hour!
Here's the first proof:
The block is 30 x 30 cm, which is the largest linocut I've ever done. Some nice effects appearing, but there's still work to be done.