I came across a fallen birch last January and harvested some fantastic bark from it.It was between 1.5 to 2mm thick and about 750 to 800mm wide when removed.The "scrappy bits" have served as fantastic firelighting material-but I have also made a few containers with some of it.
this picture above shows some of the birch bark tubs, along with a couple of other bark containers.
picture below: these are all birch with cherry tops and bottoms and handmade honey suckle twine loops.
this is just one I had a go at decorating but wished I hadn't! it does at least give a bit of scale.
I had to scrape off some of the inner bark and odd bits of "skank" ( manky bits!) before doing anything else with the bark, then laid it out between sheets of "sugar paper" with a couple of fairly heavy planks of wood on top. This was because it had a tendency to curl tighter as it dried out.
To make them, I made a pattern from heavy cardboard, then used this as a template to transfer the pattern to the bark. Cutting out was an adventure, I used my chip carving knife as the blade is short, straight and extremely sharp. I cant remember now where the pattern came from, it might have been one of Ray-vons books I think. Anyway it's a bit of a faff getting all the tabs to fit into each other but once there, they lock and you can then fit the base.I used waterproof pva for these ones but you can bore small holes through the bark into the base and then knock tiny pegs or pins made from oak or some such and this will hold the bark and base together.
The top picture also shows an ash bark water carrier on the right hand side, this was stitched with spruce root, then I waterproofed the stitching with pine resin/charcoal mix. This is very effective and strong and you could probably use the resin mix rather than pva on the birch pots. The problem is keeping the resin mix soft and sticky, long enough to clag everything together.
One note of caution: before you start to cut your bark, do a few "dry runs" with card board first! I ended up with a few "extra neat" bits of shavey tinder bark before getting the hang o f it:11doh:
Anyway, I hope this helps-Oh one more thing; if your bark seems a bit thin, you can always laminate it, sticking a couple of thinner sheets together-this might also help in making your pots watertight.
Best wishes
R.B.