I have used plain grass clippings in my garden before we do any planting or tilling, but I found an awesome recipe for “grass clipping tea” on The Garden Glove. Here are their instructions for it…
1 Five gallon bucket filled with fresh grass clippings.
Cover with water
Allow to sit for 3-5 days. Dilute the strained fertilizer tea by using one cup tea mixed with 10 cups fresh water. Pour onto soil.