In a large casserole dish sprayed with PAM, layer slices of corned beef (the thin sliced - not chipped - works best). Kind of scrunch them up with an "uneven approach" so it's not a slab of corned beef.
Drain saurkraut of 1/2 its juice and lay atop corned beef (if you like the sweeter variety of kraut, thoroughly rinse off canned/jarred juice and replace with a bit of cool water -- toss 1/2 tsp Brown Sugar Twin or Splenda into it before adding to the casserole dish.) Top with swiss cheese layer and bake at 350?F for 15 minutes or until cheese is melty but not liquidy.
While dish is baking, in separate bowl mix Thousand Island Dressing, Mayonnaise, and Relish.
Remove casserole dish from oven, slice in 4 serving-size squares and top with dollops of dressing mixture.