The language I'm constructing is supposed to be in a society on the technological level of around the neolithic revolution. The written form is (mostly) for rituals, protective amulets, etc.
The writing is carved into wooden tablets, long and vertical. The tablets can have a hole at the top, to put a leather cord through. That way they can be hung up somewhere, or multiple tablets can be arranged in a certain order. So:
Did we back then have tools to make such tablets and drill/carve holes in them? Did they have knives/blades strong enough to carve the runes in the tablet? How would the tools influence minimum size of the tablets? Would a cord of braided leather strips be strong enough to carry them?
A neolithic technology could definitely handle this simple task.
You use a stone or wooden froe to split wood with its grain, after cutting a guide groove with a stone blade. A froe is what you use to make bowstaves and shingles. You set its edge on top of the end grain and whack it with a wooden mallet. You can split wood pretty thin with the grain. You cut smaller pieces with a saw made of notched stone or of stone flakes set in a groove on a stick. You make the hole with a stone or bone awl and cut the signs with a stone or bone burin.
The wood is going to influence the signs used. Consider all the futharks of runes the letters were shaped so they could be written in the dirction of the grain without splitting the wood. All the uprights were going across the grain, and there were no horizontals, only two angles to the grain.
Braided leather was used for ship's rigging. It depends on how thick you want it.