Clean clam shells. With a scrubby, run under water and scrub the outside of each shell, well, then rinse and set aside. Do each shell until all 12 are cleaned and rinsed off.
I did (6) clams at a time, straining the liquid through a coffee filter in a colander into another pot to cook the remaining (6) clams, but if you have a pot big enough to hold all 12 clams in a single layer, you can cook all 12 at once. Place clams in bottom of pan, in a single layer. Add: about 1/2 to 3/4 cup water, 2 tablespoons butter, 1 clove garlic, minced, 1/4 cup dry white wine, 1 tsp dried oregano. 1 teaspoons dried parsley, 1/4 teaspoon crushed red pepper flakes (optional).
Cover and steam until clam shells open, somewhere's between 5 - 10 minutes.
Remove clams and again strain the clam liquid through a coffee filter in a colander. Separate shells, by twisting and pulling apart. Trim edges where connected with knife to smooth shell edges. Set aside.
Chop clams, set aside. Open can of diced clams, set aside.
In a large frying pan, melt butter with olive oil over medium heat. Stir in onion and celery, cook until translucent. Cook scallops in a separate pan till almost done. Then stir chopped clams, add can of diced clams with liquid, chopped crab meat, cooked scallops with any liquid, chopped shrimp, parsley, lemon pepper, into the onion and celery mixture. Reduce heat to low, and add bread crumbs, then slowly pour in strained clam juice from cooked clams until mixture is slightly sticky, but not wet. The bread crumbs will continue to absorb moisture, you don't want to add too much clam juice or it will be too mushy.
Fill each clean clam shell with mixture, pressing tightly into shell. Arrange on a baking sheet, and sprinkle lightly with paprika.
Bake in the preheated oven for 20 minutes, or until golden brown and sizzling.
If frozen, bake at 350 degrees F for 30 minutes, or until warmed through. Serve warm on a platter with lemon wedges. Servings: 12.