Clear a spot to grow large leaf basil in full sunlight. Find a location with well-draining soil.
Add at least 2 inches of organic matter, such as compost, peat and manure. Work this into the soil to a depth of 6 inches.
Sow one large leaf basil seed 1/8-inch deep every 8 to 10 inches. Space rows 18 inches apart.
Dampen the soil and water as needed to maintain moist conditions until seedlings emerge in one to three weeks. Continue to supply water weekly throughout the growing season in the absence of rain, or as needed to maintain evenly moist soil.
Pinch the basil plants throughout the growing season. This encourages bushier plants.
Cut the basil plants down by six leaf sets, leaving only two leaf sets on the plants. This keeps the plant from producing flowers.