Preheat the oven to 180 degrees Celsius, or 356 degrees Fahrenheit.
Salt your mandolined zucchini generously, and place it in a colander over the sink. Allow to sit for 15 or so minutes. Salt draws moisture out of the zucchini, which will make sure the tart isn't too soggy.
Place your halloumi in the glaze, and allow to sit while you assemble the galette.
Sprinkle a bit of additional tapioca flour on the base of the pastry. This will assist a lil in absorbing the moisture from the zucchini.
Lay some herbs on the bottom of the tart (otherwise they get burnt) and then start arranging the thin potato, zucchini and halloumi slices in a circle, leaving space the tuck the pastry up around the edges.
Once finished, use the baking paper to pull the pastry up over the edges of the vegetables. Press gently to secure the pastry to the vegetables.
Drizzle over the remaining glaze, and, if you fancy, finish the galette with an additional fine grating of cheddar and/or some lemon zest. Brush the pastry with a well beaten egg, to make it brown and glossy.
Transfer to the oven, and cook for around 30 minutes, or until the innards are cooked and the pastry is golden. Allow the galette to cool for 10 or so minutes before handling or serving - it is very delicate, but firms up when cooled.