In a large bowl, mix flour, sugar, yeast and salt.
Heat water to 120-130 degrees and add it to the flour mixture.
Mix to form into dough,
Knead on a floured surface and form into a ball.
Cover the dough and let it rise for an hour until it has doubled in size.
Return dough to a floured surface and divide into 8 equal portions.
Preheat a grill or stovetop griddle on medium-high heat. Roll out each dough ball into a thin flatbread, about ¼ inch thick. Brush one side of the flatbread with olive oil. This will prevent it from sticking to the grill.
Cook dough on a hot grill for 2-3 minutes on each side. Turn flatbread over when the dough starts getting darker and appears cooked.
When the bread is cooked, remove from grill and spread on pesto. Cover with sliced mozzarella and sun dried tomatoes.
Return to grill and set heat to low. Shut the cover and leave the flatbread in for a few minutes until the cheese starts to melt.
Remove the flatbread from the grill and place on a cutting board. Slice the flatbread into smaller pieces and serve while they're warm.