Mix the garlic, Italian seasoning, salt, and olive oil in a small bowl, until a thick paste forms. Rub the paste all over the pork shoulder and put it in a small roasting pan. Roast for 20 minutes. Reduce the oven temperature to 350 degrees F and continue to cook until tender and an instant-read thermometer registers 145 degrees F in the thickest part of the roast, about 50 minutes to 1 hour. Remove the pork from the oven to a cutting board and let rest 20 minutes. Cut the porchetta into thin slices.
Slice each piece of focaccia bread in half horizontally. Combine the mustard and apricot jelly in a small bowl. Spread both halves of the bread with the mustard mixture. Put 1 slice of provolone and a few slices of porchetta on the bottom half of the bread and top with the second piece of focaccia. Repeat with the remaining ingredients. Arrange the sandwiches on a serving platter and serve.