Preheat oven to 400 degrees
In a baking dish lined with aluminum foil, combine tomatoes, olive oil, garlic, and balsamic vinegar. Mix to coat tomatoes.
Bake for approximately one hour, stirring occasionally. The tomatoes are done once the liquid in the baking dish is gone. Let cool.
In a food processor, combine feta, lemon juice, and garlic. Pulse until smooth.
Add half the olive oil and pulse until combined. If the mixture is too thick or grainy, add in the rest of the olive oil and pulse a smooth paste is formed.
In a small bowl, mix together hummus and sun-dried tomatoes.
Toast bread and spread 1/4 of the feta spread on four of the slices. On the other slices, spread 1/4 of the hummus on each. Scoop tomatoes onto the hummus bread and top with 1/4 cup spinach followed by the top slice of bread (with the feta). Repeat for the next three sandwiches.