1. Rinse and sort beans according to package directions. Place in a large Dutch oven; add water to 3 inches above beans. Cover and let soak 8 hours. Drain.
2. Preheat oven to 500°. Spread chiles in a single layer on a baking sheet; toast 1 to 2 minutes or until chiles puff and become fragrant. Cut chiles open with kitchen shears; remove seeds. Cut off stems.
3. Tie oregano bunch with kitchen string. Return beans to Dutch oven; add oregano, chiles, cumin, and 1 1/2 qt. hot water. Bring to a boil over high heat. Cover, reduce heat to low, and simmer, stirring occasionally, 2 to 2 1/2 hours or until beans are tender, adding more water as needed.
4. Remove oregano and chiles from bean mixture; discard. Spoon beans in a single layer on a baking sheet; cool completely (about 40 minutes). Cover and chill 3 hours.
5. Sauté onion, jalapeños, and garlic in 3 Tbsp. hot oil in a large skillet over medium-high heat 8 to 10 minutes or until onion is tender and slightly charred.
6. Toss together beans, sautéed vegetables, green onions, vinegar, 1/4 cup oil, and 2 Tbsp. kosher salt in a large bowl.
7. Toss together jicama, cilantro, lime juice, and remaining 1 tsp. salt. Serve over bean salad.