Line a large cookie sheet (that will fit in your freezer) with parchment paper. To slice the peaches, cut in half vertically around the pit. Remove the pit. Cut the peach halves into ½-inch slices.
Lay the peach slices on the prepared cookie sheet in a single layer. Place the whole cookie sheet into the freezer until the peach slices are frozen, about 3 hours or overnight.
Transfer the frozen peach slices to a freezer bag and remove as much air as possible. Your frozen peaches are now ready to store in the freezer. Frozen fruit lasts in the freezer for up to 8 months.