Preheat the oven to 200 F, with the rack positioned in the lower third of the oven.
Set a cooling rack on a large baking sheet. Since you'll have more pineapple slices than can fit on one rack, you can stack several cooling racks on the same baking sheet by using balls of aluminum foil as "risers" between each rack.
Cut the top and bottom off the pineapple. Slice off the rough peel, then use a paring knife to remove the "eyes". Be sure to leave the pineapple core intact.
Lay the pineapple on its side and cut very thin slices, as thin as you can get them, about 1/16 of an inch thick. Pat the excess moisture out of the pineapple slices with paper towels, then arrange the slices on the cooling racks.
Bake the pineapple slices for about 2 hours, rotating the pan halfway through. If you sliced them thin enough, they should feel pretty dry after two hours, with the edges getting crinkly and golden brown.
Remove the pan from the oven, and immediately press the hot pineapple slices into a cupcake pan (a mini cupcake pan with 24 cups works very well) to mold them into a cupped flower shape. If you don't work quickly, they will stiffen up and won't easily conform to the cups. If this happens, return the baking sheet to the oven for a few minutes to soften the pineapple up so you can mold the flowers.
Let the pineapple cool completely. Initially, the flowers will be slightly crisp as they cool, but they do tend to soften up again as they sit. Keep the flowers in the cupcake pan until you're ready to use them, to help them maintain their shape. It's not advised to make the pineapple flowers more than 24 hours before you'll be using them.