Preheat oven to 400°. Line a rimmed baking sheet with parchment paper.
In a medium bowl, stir together sausage and cheeses.
On a lightly floured surface, cut dough into 12 equal portions. Using a rolling pin, roll out each dough portion to a ¼-inch thickness.
Using a 2-teaspoon levered scoop, portion sausage mixture into center of each dough portion. Referring to how-to photographs, and working with one dough portion at a time, fold dough edges over filling into one central point, pinching edges together to seal bun (Photos 1 to 7 below).
On a clean work surface, arrange 3 twine pieces in a crisscross pattern, intersecting at center of twine (Photo 8). Center one bun, smooth side down, on top of twine (Photo 9). Working with one twine piece at a time, bring opposite ends of twine pieces together over bun and tie together snuggly, but not too tight, or it will tear dough (Photos 10 to 12). Trim excess twine and place knot-side down on prepared baking sheet. Continue with remaining twine and buns.
Using a pastry brush, lightly coat buns with olive oil and sprinkle with garlic salt.
Bake buns until golden brown, approximately 10 minutes. Let cool slightly before clipping and removing twine from buns. Serve buns warm with marinara sauce on the side.
Garnish with oregano, if desired.
Recipe by TeaTime Magazine at https://teatimemagazine.com/mini-stuffed-pizza-buns/