I did these the other day - an idea I had been playing with - some of which were sent to my parents for their Christmas Gifts - made with shredded flax and shells from one of the local beaches...
I am VERY much into natural products, things that preserve - and don't harm our environment in their creating or their disposal, and that influence is becoming more and more important to me the older I get so I love the idea of creating an artwork like these using 100% natural and biodegradable things to work with that will benefit the ground when they eventually return to it.
Currently i have several palm tree spathes soaking in the bath also - the word is getting out that I am making lovely containers with them and the other afternoon I woke to find some Kind Person had dropped some off on the porch ready for me to use (thanks).
You soak them to soften the wood so it becomes flexible and also so you can pierce holes in it more easily. The water laden wood seems to 'fold around' whatever you are piercing it with rather than splitting lengthways so you get a smooth hole, not a tear, in the wood.
Thankfully this person had also copped off the fronds for me which makes them much easier to work with - this one in the bath is not pre chopped and was very hard to remove the main frond stem.