Toast: Preheat oven to broil. Slice baguette diagonally into ¼ inch slices and arrange on a baking sheet. Brush tops with 2 Tbsp of oil. Place in the middle of the oven and broil for 5 minutes, or until tops are golden brown (watch closely, they can burn quickly).
Tomatoes: Meanwhile, combine chopped tomatoes with remaining 2 Tbsp of oil and 2 of the cloves of minced garlic.
Avocado: Scoop the flesh of each avocado into a bowl and mash with a fork. Stir in remaining 2 cloves of minced garlic, basil, salt, and pepper.
Assemble: Spoon avocado mixture onto each toasted baguette piece, mashing with a fork to create an even layer. Top with tomato mixture. Optionally top with more fresh basil, a drizzle of balsamic reduction, and/or flaky sea salt.
If making ahead, store all components separately until ready to assemble. Can be made 1 to 2 days ahead.