I glued a section of 1 X 3 to the freezer and then hung the drip tray from screws in the wood. Worked just fine for me:
A side benefit to using the 1 x 3 is that it centers the drip tray more directly under the taps. I roughed up the paint on the freezer with sandpaper and used Gorilla Glue to attach it. A little tub and tile adhesive caulk around the edge of the wood gave it a more finished appearance.