Toast the bread. Trim the crusts. Halve the slices into 1 1/2-by-3-inch pieces.
For the prosciutto and ricotta: In a small bowl, mix together the ricotta, olive oil, lemon zest and salt. Spread the mixture on 6 pieces of bread. Ribbon a piece of prosciutto on top and garnish with 2 arugula leaves.
For the avocado: Place 2 slices of avocado on 6 pieces of bread. Sprinkle evenly with the quinoa, sea salt and chile flakes.
For the smoked salmon: In a small bowl, mix together the creme fraiche and capers. Spread evenly over the remaining 6 pieces of bread. Ribbon a piece of salmon over the top and garnish with 1 or 2 batons of chive.
Rinse 1/2 cup quinoa under cold running water. Heat a medium skillet over medium heat. Add the damp quinoa to the pan and cook, stirring often, until the quinoa is dry, lightly brown and beginning to pop, 5 to 7 minutes. Remove the pan from the heat and pour the quinoa onto a large plate to cool completely. Store in an airtight container in the refrigerator for up to 5 days.