Preheat oven to 400 degrees F with the rack in the middle. Arrange on a baking tray in a single layer, brush top side with olive oil. Toast about 5 minutes.
Ceviche: In a small glass bowl add the shrimp, olive oil & lemon juice. Add a pinch of garlic salt. Mix gently so all combine well. Chill mixture in the fridge for 20 minutes. Shrimp should be white when well marinated.
Guacamole: Mash avocados with lemon juice. Season with garlic salt & pepper. Add onion & tomato.
Assemble: Top each baguette with guacamole, tomato slice, shrimp ceviche & cilantro.