Arrange bread slices on baking sheet in a single layer. Drizzle each slice with a teaspoon or so of olive oil. Bake 8-10 minutes until golden brown. Remove from oven to cool.
Meanwhile, with your food processor running, drop garlic clove down chute to mince. Scrape down sides of food processor bowl. Add next 3 ingredients (feta through olive oil) and pulse until smooth and combined - the texture here is up to you. Pulse fewer times if you want to have larger chunks of feta, more times if you want a smoother consistency.
When bread slices have cooled, spread a generous amount of feta and lemon spread on each one and place on a serving platter. Drizzle crostini with olive oil and sprinkle with crushed red pepper flakes and reserved lemon zest. Serve.