Wash the tomatoes and allow them to drain and dry.
Cut out the stem end and slice off the blossom end.
Slice the tomatoes into 1/3-1/2 inch slices.
Arrange the slices on a cookie sheet, one layer only. Do not overlap the slices.
Place in the freezer until the slices are solid, for about 2-3 hours.
Pop the slices loose from the cookie sheet with a spatula and place the slices in freezer bags.
Lay the bags on the cookie sheet. After a couple more hours in the freezer, these bags can be stacked on one another.