Clay

[Kokaiin]

So, I'm looking for clay to make a cauldron to make bone glue to make palisades. Problem is, I never find any. I dug in the shallows of the rivers, and only found one piece, the first time I dug for it. Then I tried mudflats and again, only found one, the first time I tried digging.

Is there some connection between me only getting clay the first time I try digging?

[Seizure]

Unless there is a quality spot nearby, you will only be able to get one piece of clay in ~10 square radius.

One thing to know about clay quality spots is that they decay from use, and they are limited. Once you use one up, you have to wait for a while for it to resupply.
I think clay is the only natural resource that runs out completely. Water and soil can be taken from infinitely, so long as you dont mind Q10 stuffs.

[Kokaiin]

Oh, OK. but I still don't see anymore clay even if I move up to 40 squares away from that one space.

[Zamte]

clay "non-spots" are fairly large. I'd imagine somewhere around a minimap across or so. If you want a cauldron, or a kiln (and you will need one) then you're going to have to grab a boat, and begin sailing down the river, stopping every minimap or so to check for clay. If you get anything higher than q10, or you get multiple pieces of q10, you've found a clay spot, and can begin digging clay from it for use in your cauldron and kiln. Keep track of where it is, as you'll be using it a lot.