Measure a 3-feet-by-3-feet area and mark it with spray paint. Dig down six inches into this area all around. Check for levelness.
Mix the mortar according to the manufacturer's directions in your wheelbarrow. Get your bricks in place so you can use the mortar immediately.
Lay your first layer of bricks around the perimeter of the area you have unearthed. Spread mortar across the bricks with a trowel and begin your second layer. Stagger the second row of bricks to provide sturdiness to your fireplace as you build up.
Continue stacking rows. Stop approximately three-feet from the hole's base. This provides enough height without making cooking difficult.
Allow the mortar to set 24 hours. Use gravel to fill the bottom of the fireplace. Place a wire rack on top of the fireplace. Use wood to start a fire and test your handiwork.