The dough could be too soft, especially if you are working in a hot kitchen. Wrap the dough in clingfilm and place in the fridge to firm up before rolling and cutting out. You can also place the tray of cut out biscuit dough back into the fridge for about 15 mins to firm up again. Just make sure your oven is up to temperature when you are ready to bake them. Make sure the ratio of flour to fat is correct, too much butter is often another reason cookies spread and flatten during baking.