Mix together the flour, oats, sugar and spices in a large bowl.
Add the butter and rub it in with your fingertips until no lumps of butter remain.
Bring the dough together and knead very lightly until it forms a ball.
Shape the dough into a log about 5-7cm (2-2 ¾ in) thick - use your hands and roll it on a lightly floured surface to get it as even as possible.
Wrap the log in a piece of baking parchment, twisting the ends tightly to form a cracker shape. Refrigerate for 1-2 hours until firm.
Meanwhile, preheat the oven to 180°C/160°C fan/350°F/gas mark 4 and line two baking sheets with baking parchment.
Use a very sharp knife to slice the log into approx 8mm thick slices. Place them spaced apart on the baking sheets.
Bake for 20-25 minutes until lightly browned around the edges and on the underside.
Allow to cool on the tray for 5 minutes then carefully transfer them to a wire rack to cool completely. Once cold store in an airtight container.