A platform-style wood deck that sits directly on the ground can be an attractive and useful addition to a walk-in garden or back yard. Build it on a level area, or as level as possible, and use concrete pier blocks to support the rim joists. In addition, use pressure-treated wood for the framing and a weather-resistant wood like cedar or redwood for the decking. If you want your deck to last, protect it from the elements with a high-quality stain, sealer or oil finish.
Level the area of of the deck with a pick and shovel. Spread a plastic moisture barrier over the ground and secure it in place with 12-inch wire staples.
Dig holes at the corners of the deck perimeter and at 6- to 8-foot intervals in between for the pier blocks. These holes should be deep enough so that two-thirds of each block is underground. Use a torpedo level to make the surface of each block level and a line level to make all the blocks on the perimeter level with each other.
Set 2-by-8 pressure-treated boards on the pier blocks to form the perimeter of the deck. Connect these at each corner by using a drill to affix 2-by-8 corner brackets with 1 1/2-inch screws. Connect the wooden perimeter to each pier block by screwing an L-bracket into the wooden top of the block and screwing this bracket to the joist. If you have to join joists, do it at the mid-point of a pier block. Join them by screwing flat joining plates onto both members.
Use 1 1/2-inch screws to attach 2-by-8 joist hangers to two of the rim joists opposite each other at 16-inch intervals. Cut joists to fit in between these rim joists and drop them into the hangers. Screw them in with 1 1/2-inch screws.
Lay the decking boards on top of the frame, perpendicular to the joists, and screw them down with 3-inch screws. If you have to join two or more decking boards to complete the length of the deck, be sure they join at the mid-point of a joist. Use two screws per joist on each board.
Finish the deck with a wood preservative, stain or varnish.