I'am educating myself to be a proper wood chop teacher, have been working as it for four years and mostly need the degree to get a steady job and decent pay.
One of the many tasks we got was to make "a box with a lid" and i interpeted that as a pocket flask since i prefer to make thing that could be useful.
You need brass, lead-free tin, a 3/8" lid, a 3/8" sleeve, some paper, sheet metal cutter and soldering torch. The lid are the same kind thats used on radiators and plumming, easy to find and usually cheap.
Step 1: The Template
Start by making a template, think about how you want it to look. A made mine with a bit of airfoil shape, it hides nicely in the pocket.
Step 2: Cut the Metal
Use glue if you want to prevent the paper from moving. Make the top and bottom a bit larger, it should be ground down later. The top and bottom are the same shape so you only need to make one.
Polish the edges of the straight piece. In the next step it should be solderd.
Step 3: Soldering
Start by soldering the straight piece and the sleeve with silver solder.
If you use tin solder here it will part when you attaches the top and bottom.
When the soldering is ready you have to clean it. I used a light acid bath to cleance the metal.
Step 4: Tinning
Now we apply lead-free tin on the inside and if you want on the outside. The brass must be absolutely clean, use steel wool to clean if necessary.
Step 5: Assembly
When its tinned its time to assembly the flask. Solder the top and bottom pieces with tin solder.
Cut of the unnecessary brass with a metal scissor. Ground the edges to the right shape.
If you tin the outside you might get a nice effect by not soldering the ground areas.
Step 6: Polish
Polish the flask with steel wool until it's good enough to give to your father. Make sure to clean it properly inside.
Use it with care, alcohol is not healthy, it's illegal to carry it in some places and times.