The making of bowls and containers including cups, enabling you to do rock boiling etc. Be certain to use a non poisonous species of tree. This can be handy as a skill when you have no container available for boiling water to make it potable, or to make a stew by boiling the contents.
In the photo you can see a partially worked log for making a bowl.
You can do rock boiling by heating up non-porous rocks and placing them in a fire, then placing them in your water filled container that you made. This will destroy any biological micro-organisms such as Giardia Lamblia and Cryptosporidium. Boiling is useful for other things as well.
Be certain that the rocks weren't taken from a stream or other body of water, because if the rocks are water-logged, the heat will cause the water in the rocks to expand and the rocks can explode. This is a very real situation that can happen, and it could take out an eye with flying fragments of sharp rock.
It takes a lot of patience, and is the kind of thing you can do at night while sitting beside your fire if you want to. You can use a split log and hollow it out using heat from coals in combination with your bushcraft knife. It is possible to hollow out a cover as well by using the other half of the log that is split. What this does is that in combination with rock boiling you may trap steam between the two halves, and cook your food more rapidly.
The log may partially
split under the heat while making your bowl, or the wood itself has
cracks in it, so that is something to watch out for. Although you can blow air
around the coals to increase and direct the heat to where it is needed
to form your bowl or use a straw if you have one, it is dangerous and I wouldn't recommend it.
Be careful because the
coals may 'pop' as it did with me. No damage done, but it gets the heart
rate going. You don't want sparks to burn holes in any synthetics you
may be wearing, or worse get a spark in the eye by blowing in it. I think that is a dangerous method and don't recommend it. Just use good hot coals and burn the wood to form a cavity to make the bowl. Keep your face away from the coals!
For more details on coal burning I have included a link here below.
1. Wood Containers - How Not to Coal-Burn a Wooden Container
For more details on rock boiling I have included a link here below.
1. Alderleaf Commons (Info + video)
Have a look at the Videos page as well for more information on coal burning.