Preheat the oven to 375°F (190°C).
Slice the baguette into approximately ¼-inch rounds. For larger crostini, cut the baguette lengthwise first and then slice it diagonally into portions.
Arrange the bread in a single layer on a baking sheet.
Lightly brush both sides with extra-virgin olive oil.
Bake for 5 minutes.
Flip the bread and continue baking for another 5–7 minutes, until lightly golden and crisp around the edges.
Remove the crostini from the oven and allow them to cool slightly.
Meanwhile, finely dice the Roma tomatoes and cucumber.
Chop the green onions and crumble the feta cheese.
In a large mixing bowl, whisk together the lemon juice, ¼ cup olive oil, red wine vinegar, garlic powder, salt, black pepper, oregano, dill, and basil.
Add the diced tomatoes, cucumber, feta, and green onions.
Toss gently until everything is evenly coated in the lemon-herb dressing.
Taste and adjust the seasoning as needed.
Spoon the Greek Bruschetta topping generously over the toasted crostini.
Garnish with additional feta, basil, oregano, or freshly ground black pepper if desired.
Serve immediately while the crostini remain crisp.