How to Make It
Preheat the oven to 325°. In a medium bowl, whisk together all of the ingredients except the ribs and salt. Layer 2 long sheets of heavy-duty foil on a work surface and set 1 rack of ribs in the center, meaty side up. Brush with 3/4 cup of the sauce and wrap tightly in the foil. Repeat with the remaining 2 racks of ribs. Transfer the foil packets to 2 large rimmed baking sheets and bake the ribs until tender, about 2 hours.
Unwrap the racks and transfer them to a work surface. Cut them into 3- or 4-rib sections.
Light a grill. Season the ribs with salt and grill over high heat, brushing with the remaining sauce and turning occasionally, until glazed and lightly charred in spots, about 4 minutes. Cut into individual ribs if desired. Transfer to a platter and serve.
Gochujang is available at Asian markets, stores like Whole Foods and amazon.com.