For smaller mosses. I use a binocular microscope, a thin razor and pretend it's
a microscopic version of slicing veggies. It helps to keep one end of the blade
steady on the slide, as if one were using a French knife.

It takes some practice, but free-hand sections work a lot better than trying to
fish lichen thalii from masses of elder-pith. At least if you're not working
with crustose apothecia.. Then one really needs a more useful technique.

Christine Manville