Begin by preparing the squash for roasting. Cut the squash in half lengthwise and scoop out the seeds. Lay cut side down in a roasting pan and fill halfway with water. Cook in a 200°C (400°F) oven for 40 minutes to 1 hour (adding more water as needed to top up), or until a fork can easily pierce the flesh of the squash. Let cool, then scoop out the flesh.
In a small bowl combine the 2 tablespoons of ground flax with 4 tablespoons water. Let sit for 5 minutes.
In a larger bowl combine 3 cups of squash with the soaked flax meal, almond flour, garbanzo flour, salt, pepper, dried oregano, and extra ground flax. Stir to combine.
Spread the mixture onto a parchment lined tray and create a 30 cm (12 inch) circle, making sure that the edges are a little bit thicker. Bake in a 220°C (425°F) for 30-35 minutes or until the edges are crisp and golden and the centre is set (and can peel away from the paper).
Top with pizza sauce, tomatoes, and olives, and bake for another 10 minutes. Let sit a few minutes before garnishing with greens.