Dissolve the yeast in 60 ml of lukewarm water.
Mix the rye flour with the yeast mixture in a bowl. Let the pre-dough rest for 15 minutes.
Mix the rest of the lukewarm water, the spelt flour, the salt and the olive oil into the pre-dough. Knead the dough for 5 minutes until it is elastic (with the dough hook in the food processor or by hand). Roll it into a ball and let it rest for 30 minutes under a damp towel.
Preheat the oven to its highest setting (250°C).
Prepare the pizza toppings.
Sprinkle the work surface with flour. Cut the dough into 3 pieces, roll them into balls and roll them out thinly.
Place a pizza base on a sheet of baking paper.
Top the pizza with the toppings.
Place the pizza with the baking paper at the bottom of the oven (so not on a rack) and let it bake for 10 minutes. Turn the pizza around a little bit every now and then, so that it colors evenly.
Slide the pizza with the baking paper out of the oven onto a plate and cut into pieces.