For the dough, combine the water, yeast, sugar and olive oil and let stand for 5 minutes until foamy. In a large bowl, mix together the flour and salt. Add the wet ingredients to the dry and stir until it forms a shaggy dough.

Turn the dough onto a lightly floured work surface and knead for 10 minutes until the dough is smooth and elastic. (Alternatively, the dough can be mixed in the bowl of a stand mixer using a dough hook.)

Gather the dough into a ball, transfer to an oiled bowl and cover. Place the bowl in a warm spot to allow the dough to rise until it has doubled in size, about 2 hours.

Preheat a gas or charcoal grill on medium high heat.

On a lightly floured work surface, roll out the dough in a 12 inch circle. Place the dough directly on the grates and grill for 3 minutes with the lid closed until the crust has grill marks and has puffed up. Turn over the crust and grill for an additional 2 minutes.

Remove the crust from the grill. Spread the tomato sauce leaving a 1/2-inch border at the edge. Arrange the mozzarella and squash blossoms on top.  Put the pizza back on the grill for a couple minutes to let the cheese melt. Slice and serve right away.