Place the vinegar and shallots in a mixing bowl. Gradually stream in the oil while whisking. Add in the oregano and black pepper, and mix. Add the okra, olives, red peppers, capers and parsley. Mix and set aside.
Split the bread lengthwise. Spread 1/2 cup of the olive mixture on the bottom slice of bread. Arrange the provolone over the olive mixture, then layer the mortadella, salami, red onions and sliced eggs.
Finish with another 1/2 cup of the olive mixture. Place the top half of the bread on the sandwich. Wrap the sandwich in plastic wrap, then weigh it down to press flat, and refrigerate for 1 hour.
Unwrap the sandwich and slice into quarters to serve.
You can substitute the hard-boiled eggs with a fried egg for each serving.