4. Build the sandwich: Halve the ciabatta laterally, and lie halves flat, cut-side up. Use your fingers to remove some of the interior crumb of the bread, being careful not to create a hole in the crust. Brush both sides liberally with remaining red pepper vinaigrette, reserving any unused vinaigrette for another use. Cover the ciabatta top side with a single layer of cucumber slices, and layer avocado over the cucumber. Sprinkle ¼ teaspoon salt and drizzle with the lemon juice. On the bottom slice of bread, arrange the drained tomato slices in a single layer. Spread the crab salad evenly over tomatoes, then close the sandwich to encase the fillings.