Determine the frost line in your area. Dig out an area equal to the dimensions of your slab (30 feet by 60 feet) down to the frost line.
Fill the hole evenly with crushed gravel until it is level with the edge of the hole. Compact the gravel firmly.
Use a laser level to ensure the final grade of the area is flat.
Creating the Form
Lay out all your long 2-by-6 boards along the perimeter of the proposed slab. Nail the long boards together into a box using 3-foot-long boards.
Measure diagonally across the box twice – once from each base corner. Both measurements should be exactly the same to ensure the slab will not be skewed.
Pound metal or wooden stakes into the ground at an angle so they rest against the form and brace it. This will help prevent the form from shifting when the concrete is poured in. Backfill some gravel along the outside of the form to help support the form and the concrete once poured.
Ask the concrete truck driver to mix your ordered concrete to a 5-inch to 6-inch slump. This will give you concrete that is easier to push around but not so wet that it weakens the mix. Put on your gloves and boots to protect your skin.
Start pouring the concrete into the form. Use the shovels and rakes to help direct the concrete to where it should go. After a quarter of the concrete has been poured, start dragging and leveling the concrete with the hand mag float. This process is called screeding. Sink the rebar along the edges until it is 2 inches under the form's upper edge. Level the concrete to the form's upper edge with the mag float.
Hammer a metal pipe into the ground at the center of the slab. Mark the pipe at the same height as the top of the form. This will be your level marker when you get to the center of the slab. Level the concrete in the center of the slab to the mark on the pipe. Once level, pull out the stake.
Start on one side of the slab, and use a magnesium screed to screed off the top of your forms and the middle pad. Use the back edge and pull the concrete down using small 6-inch to 8-inch strokes. Do the next side in the same manner to get the concrete level. Do not try to smooth the concrete yet. Simply focus on making it level. Continue pouring the rest of the slab in quarter sections using the same techniques as for the first section.
Once the slab has been screed, push and pull the bull float over the surface of the concrete to fill in any cracks and holes or push down any pebbles at the surface. This will also allow the finer particles of the cement mix to rise to the top and provide a smooth surface.