This recipe comes from the very talented Gingerbread Snowflakes. You should really go over to her blog becaue she has a step-by-step photo tutorial.
12 slices of bread - white or wheat
About 1 cup each of three of your favorite sandwich fillings -possibilities are egg salad, deviled ham, cream cheese flavored with dill or black olives, pimento spread, or layers of grape jelly, cream cheese and strawberry jam, or peanut butter and two kinds of jelly- whatever you want
Place one piece of bread on your work surface and spread on a thin layer of soft butter. The butter layer is necessary to prevent the fillings from soaking into the bread.
Spread a good amount of your sandwich spread over the slice of bread making it as even as possible.
Butter one side of a second slice of bread. Place the buttered side down on top of the bread with your spread on it. Keep doing this layer, by layer, always buttering both sides of the bread, until you have used four slices of bread and three fillings. The top and bottom of the sandwich remain unbuttered. Repeat with remaining bread and fillings. You will wind up with three ribbon stacks. Now wrap your sandwich stack in plastic wrap and store at least 18 to 24 hours in the fridge.
When ready to serve, unwrap and use a serrated knife to carefully cut off the crusts. Don't push down as you cut - just a gentle sawing action as you cut through the layers. Remove all four crusts and set aside for a midnight snack later! Or if you are starving, nibble as you work. Now slice your rainbow sandwich into about 6 slices (1/2" thick) and then cut each slice in half. You should get about 12 small ribbon sandwiches out of each stack or 36 in total. Or don't cut in half - just leave them as large ribbon sandwiches!