Crush the garlic cloves into small pieces using a mortar and pestle.

Add olive oil, salt, oregano, and black pepper to the crushed garlic.

Mash the mixture into a paste.

Make 12 deep incisions a few inches apart in the pork shoulder roast using a sharp knife.

Pack the seasoned garlic paste evenly into the incisions and over the entire roast.

Transfer the roast to a large bowl.

Pour red wine over the roast, ensuring it is completely covered.

Cover the bowl with plastic wrap.

Marinate the roast in the refrigerator for 24 hours.

Pour out the red wine marinade.

Place the roast fat-side up in a roasting pan.

Cover the roasting pan with aluminum foil.

Let the roast sit at room temperature for about 30 minutes.

Preheat oven to 400 degrees F (200 degrees C).

Place the roast in the preheated oven and immediately reduce the temperature to 300 degrees F (150 degrees C).

Bake for approximately 4 hours, or until the center is slightly pink.

Increase the oven temperature to 400 degrees F (200 degrees C).

Uncover the roast and continue baking for about 1 hour, until the fat is crispy and an instant-read thermometer inserted into the center reads 160 degrees F (71 degrees C).

Remove the roast from the oven.

Let the roast rest for 20 to 30 minutes before carving.