An inner bag holds the food, and an outer bag holds enough water to
displace the air around the food.* There are two zips at the top of
the bag, one for the food, and once for the water. Once the air is
evacuated, the entire package is frozen in a tray to give it a uniform
shape that can be
stacked.
A one-way valve from the inner bag to the atmosphere would be
great, because then you could squish the water bag around to
displace all of the air.
This system eliminates the need for vacuum pumps and special
plastics. Because the inner bag could be pretty thin, this may use less
plastic than normal zip freezer bags. The ice would help protect
against freezer smells.
* I did this with 12 ounces of 3/4-inch cut raw chicken breast (for
stir fry), and two cheap storage (not freezer) bags. I doubled the
bags, and left a little opening in the bag that held the chicken, and
filled the outer bag with water. This displaced the air from the
inner bag, which I then sealed. Then I sealed the outer bag and put
the whole thing in a small square cake pan.
The result was a very square block of thin ice with chicken in the
middle. When I needed it, I ran it under water, which loosened the
outer bag. I removed this, and the ice broke away from the chicken
easily. The chicken was very frozen, with no sign of freezer burn or
crystals.