Pour the concrete into a wheelbarrow and add some water. Using your spade, mix the concrete and water together. Add more water or concrete as you need to get a thick, toothpaste consistency. To create the slab, pour your concrete mix into the footing that you dug out earlier. Leave enough space at the top to fill in later. Now it’s time to level off the concrete slab. Start by using your spirit level to even up the concrete mix. Once the level of your slab is even, take the trowel and use it to smooth over the concrete mix. Then leave it to set for 24 hours.