Before you roll out the dough you need to make the filling. Add the diced strawberries to the strawberry jam and mix until well combined. Set aside while you roll out the dough.
Turn the dough out on to the counter. It shouldn't be sticky and be easy the handle. Do not use flour when rolling out the dough.
Gently roll the dough out into a rectangle. 60cm x 30cm is a good size to aim for. It doesn't have to be perfect, but the bigger you an get it, to more perfect strawberry swirls you will get.
Spread the filling all over the dough, leaving a 10cm gap on one of the long edges. You need to leave a gap so that dough will stick to itself when you roll it.
Once the filling is spread, roll the dough into a log, starting on the opposite long edge to the gap you've left.
Roll the dough into a tight log, using the unfilled dough to seal the log. You can spray a little water on the part where the dough joins if you want to - but the dough should stick to itself without it.Lay the log out with the seam underneath. Cut the log into approximately 10 pieces (you can measure and divide by 10 if you want them to look even - or just go freehand if you're not too fussed). As you can see in the photos, I have not measured these at all. Using dental floss to cut them will help you keep their shape and give the strawberry rolls a flat surface, however a knife is fine if you don't have any dental floss.
Place the sourdough strawberry rolls into a cast iron skillet lined with baking paper. Face all the seams inwards so that they don't unravel. If you don't have a cast iron skillet, a baking tray or casserole dish is perfectly fine. They don't have to touch as they will once the dough is puffy.