I have some round slabs of wood.

I would use a outside urelane finish all the way around. They would make a gorgeous walkway

Rub linseed oil on them.

https://www.preservation-solutions.com/wood-treatment-products/wood-treatment-product-guides/stabilizing-a-cross-cut-section-of-wood-with-pentacryl/

What kind of wood are they? Where did they come from, for example slices from a trunk, etc.

Having experience living in an area with lots of snow, I would caution you against using them for a walkway until you know for sure that they have been treated for exterior use. It is not so much the cold temps, but moreso the constant moisture, and lack of drainage that would cause problems. One winter of 5 months or so of snow, they will eventually just rot otherwise.

As for shoveling, if you don't get the pieces level and anchored very securely, they will likely start to move, will be a pain to try to shovel around, and a tripping hazzard.

Don't know if this may, or may not be, an alternate option of how to use the pieces, ..... but I just saw an idea of making snowmen out of log slices.

In the search box in the upper left hand corner of the page, type in Snowman made from logs.