Place a small, thin mound of baby greens, slightly wider than the mold onto the serving plate. Do not place too many or make the mound too thick, you want your crab stack to set comfortably on top.
Place the mold in the center of the mound of greens, so that greens show all around (See photo above).
Starting at the top, with a very sharp knife, cut down into each avocado until you hit the pit. Cut completely around the avocado, top to bottom, touching the pit the entire time.
Pull the two halves of the avocado apart and remove the pit with a spoon.
Use the spoon to scoop the avocado out of the skin.
Slice into thin strips.
Gently push down the avocado slices into the bottom of the mold.
In a small bowl, mix together mango, jalapeño, red bell pepper and red onion.
Gently push mixture down on top of the avocado layer.
In another small bowl, gently toss crab with the refrigerated yogurt mixture.
Gently push down on top of the mango layer.
Carefully slide the mold off of the stack. Place plate in refrigerator to chill until ready to serve.