Combine the fennel, flour, salt and starter in a large bowl. Dissolve the crumbled yeast and honey in the water then mix into the dry ingredients with the dough hook attachment until combined.
Turn out onto a floured work surface and knead for about 10 minutes by hand. Transfer to a bowl, cover and let rise in a warm place for at least 45 minutes.
Preheat the oven to 500°F with a pizza stone or inverted baking sheet inside. Knead the dough briefly on a floured work surface then divide into 3 pieces. Roll out each piece until about 18 cm (approximately 7 inches) diameter. Place on a baking sheet lined with parchment paper, stab several times with a wooden skewer and sprinkle with a little rye flour.
Cover and let rise for 30 minutes in a warm place. Slide a small baking pan filled with about 250 ml (approximately 1 cup) boiling water into the oven. Place the flatbreads in the oven, reduce the heat to 190°C (approximately 375°F) and bake for about 30 minutes.