This type of ‘cooker’ has been used in Scandinavia since time immemorial, and is an alternative to other forms of camp cooking over a conventional type of fire.
Although seeming relatively simple fuel economical way of cooking/heating water it does require an understanding of the fire triangle of ‘oxygen, fuel and flame’.
In the Scandinavian countries the predominant wood is, of course pine trees. Pine being a very resinous wood will burn whether seasoned or fresh cut. Other woods need to be seasoned to work well.
Communication and team work, who is doing what and when is essential.
Ensure your log is round enough to sit your kettle/pan on.
Make sure the base of the log is secure (you don’t want to spill your stew!)
Make the cross-cut deep and wide enough to allow air circulation.
Prepare your fuel before lighting anything.