Welcome to the forum Brangdon.
The problem is not forming the container or setting it up on a fire. The problem is removing the foil from your kit, unfolding it and finding "pinholes" in the corners where the foil was folded.
Here are some pictures from a test I conducted.
I started with a single sheet of 12"x12" (30.48 X 30.48 cm) heavy duty aluminum foil. I formed the basic shape by folding the foil over my knee:
![](http://img.photobucket.com/albums/v336/Hutch4545/01_BASIC_SHAPE.jpg)
I then used my thumb to flatten out the bottom of the container to make a base:
![](http://img.photobucket.com/albums/v336/Hutch4545/02_FORM_FLAT_BOTTOM.jpg)
And folded the top of the foil over to add strength to the creased sides:
![](http://img.photobucket.com/albums/v336/Hutch4545/03_TOP_EDGE.jpg)
Next I filled with 18 ounces (540 ml) of liquid. (I used iced tea for color contrast)
![](http://img.photobucket.com/albums/v336/Hutch4545/04_ADD_LIQUID.jpg)
I then placed the filled container on the stove:
![](http://img.photobucket.com/albums/v336/Hutch4545/05_ONSTOVE.jpg)
After a few minutes, a full boil:
![](http://img.photobucket.com/albums/v336/Hutch4545/06_BOILING.jpg)
In the field, I have had success with variations on the types of fires highlighted in green:
![](http://img.photobucket.com/albums/v336/Hutch4545/07_USABLE_FIRE_SHAPES.jpg)
Probably the easiest and my favorite is this variant:
![](http://img.photobucket.com/albums/v336/Hutch4545/08_FIRE_DIAGRAM.jpg)
As far as the pinholes in the folds of the foil - well we'll just have to keep experimenting. [color:"pink"] [/color]