The base of this pot pie is filled with good for you veggies. (catchingseeds.com)
I cut a circle (ish) bit of the plastic bag to wrap around the base of the pot. (serenitynowblog.com)
Just a note: I don't have a canning pot and rack like described in the above links, so in the canning class I took last summer, the instructor said you could use any large stockpot and line the base of the pot with a couple dish towels. (sharedappetite.com)