Kolrosing is one of those great “peasant” crafts in which you can get amazing results with a bare minimum of supplies. Basic form – seal the wood, incise a line in the wood, rub in bark dust or soot, then sand and wax to hold the colorant in.
I’ve got a nice Pinewood Forge kolrosing knife, but you can use a chip-carving knife or an X-acto. Cinnamon is technically bark dust, and super easy to find; powdered instant coffee works too, or a bit of tree bark rubbed over sandpaper. This spoon is a birch “disposable” spoon you can find in bulk on Amazon, for a test piece, but the technique works on any piece you have in mind.
Not saying the technical skill displayed here is amazing – but I am certainly tickled at my own pun.