Hi, First time poster, so I dont know if I have the correct forum so Im looking to buy or build a wooden outdoor play set which requires a level, rectangular area. The finished area would be approximately 25 x 15. Our back yard has a slight grade in two directions (to the rear and to the right). The grade drops approximately one foot per 25 feet of length and width. Instead of cutting or excavating into the grade, I want to build the surface above the grade. My plan is to build a perimeter using landscape timbers and filling this in with soil and then topping it off with mulch or pea gravel. Im not sure how to get started on this. Do I start from the lowest corner and work out in both directions? Any ideas would be appreciated. Thanks.