In a large bowl, combine olive oil, smoked paprika, garlic powder, onion powder, cayenne pepper, dried oregano, salt, black pepper, and additional cayenne pepper if desired. Mix well to create a spice rub.
Add the chicken thighs to the bowl and coat them evenly with the spice mixture. Let the chicken marinate for at least 30 minutes (or up to 2 hours in the refrigerator for more flavor).
Preheat a grill or skillet over medium-high heat. Cook the chicken thighs for about 5-7 minutes per side, or until the internal temperature reaches 165°F and the chicken is nicely charred.
While the chicken is cooking, mix mayonnaise and hot sauce in a small bowl to create a spicy mayo.
Once the chicken is cooked, remove it from the heat and let it rest for a few minutes. Slice the chicken into smaller pieces that will fit on the slider buns.
To assemble the sliders, spread a layer of spicy mayo on the bottom half of each slider bun. Add a piece of blackened chicken, followed by shredded lettuce and a slice of tomato. Top with the other half of the bun.
Serve immediately and enjoy your spicy blackened chicken sliders!