Turn the slow cooker to the "low" setting.
Rinse the pork in cold water, then dry completely. Sprinkle 1/4 tsp. salt and 1/4 tsp. pepper on top side, and press into the pork using your hands or tongs. Sprinkle remaining 1/4 tsp. salt and 1/4 tsp. pepper on bottom side, and press into pork.
In a small bowl, whisk together all of the cumin, oregano, and paprika. Sprinkle half of the spice mixture onto the top of the pork loin. Drizzle 1 Tbsp. of olive oil directly onto the seasonings, and gently press the olive oil and spices into the pork (you can use your hands or tongs for this, too!). Repeat on the bottom side.
Once all of the pork is seasoned and coated with olive oil, place it into the slow cooker. Be sure the fattier side is facing up.
Add jalapeño, garlic, and onion. Also pour in the orange juice and beer.
Cover and cook for eight hours. If you're home during the cooking process, feel free to flip the pork over after a couple of hours. The pork should shred apart very easily when it is done. (You can let it cook past eight hours if it isn't shredding apart easily!)
Shred the pork directly in the slow cooker, and allow it to soak up any excess liquid.
In a saute pan over medium-high heat, sear the pork until it darkens in color and develops a crispier exterior. Serve it directly onto the slider buns, then top with creamy tex-mex sauce.