Toast the bread. In a small bowl, mash together the avocado, lemon juice, and red pepper flakes. Season to taste with sea salt. Top two slices with mashed avocado and drizzle with olive oil. (Top with smoked salmon and thinly sliced lemon if you like.)
Top the other two slices with ricotta, a sprinkle of sea salt and a drizzle of olive oil. Sprinkle with roast tomatoes and basil, and a slice of prosciutto and a few arugula leaves, if desired.
NOTE: These are best eaten immediately. If you’d like to pack them for lunch, omit the toasting. On the avocado toasts, I like swapping out the salmon for roast chicken, and adding shredded veggies like red cabbage and carrots.