Brush baguette slices with 2 TB OO and bake for 10-15 minutes at 375 degrees
Remove baguettes and raise oven to 400 degrees
Put grapes on parchment lined baking sheet and toss with remaining 2 TB OO and the rosemary and thyme and bake for 25 minutes at 400 degrees until wilted or blistered
While grapes are cooking mix ricotta cheese with salt, pepper, and red chili flakes
Put one heaping teaspoon or so of ricotta mixture on each crostini
Add cooked grapes to each ricotta crostini and top with lemon zest and small amount of finely chopped walnuts
Drizzle each prepared crostini with reduced balsamic vinegar