Toast bread and prepare bacon according to directions on package.
Combine crab, avocado, mayonnaise, lemon juice and splash hot sauce in a small mixing bowl. Mash gently with a fork until all ingredients are incorporated together and there are no large lumps.
Spread a generous spoonful of crab salad on one piece of bread. Layer fresh baby spinach, sliced tomatoes, and bacon. Spread a thin layer of mayonnaise on another piece of bread to complete the sandwich.