Unscrew the bolt head and remove the extractor screw, extractor and spring. Simlicity itself
Remove screw from rear of cocking piece
Make special tool shown in 'home made tooling for your Lee Enfield' thread and unscrew striker. Remove striker and spring
Make sure you note the exact position of the rear of the striker in relation to the rear of the cocking piece so that it goes back in the same relative position.

Easy as that.......