Pat shrimp completely dry using paper towels and place in a large bowl. Sprinkle with Cajun seasoning and toss to evenly coat. Heat oil in a large skillet. Once the oil is warm, add the shrimp and cook for 2–3 minutes on each side, or until the edges are golden and the center is cooked through.
While the shrimp cook, mash the avocado. Then add lime juice, salt, cilantro, and onion. Stir until combined.
Place cucumber slices in a single layer on your serving dish. Cover with a dollop of guacamole, then place a piece of shrimp on top. Sprinkle the top with additional cilantro and the smashed cheese crisps.
Serve immediately.