Cut and Notch the Timbers
Cut the landscaping timbers (Image 1) to size.
(32) pieces at 42" long (for the back and side walls)
(20) pieces at 14" long (for the front)
(2) pieces at 60" long (the top side pieces that will hold up the front porch)
Set the table saw to 3" wide and run all timbers through so they are all a uniform thickness. Flatten the top, bottom and inner sides so the timbers will fit together easily. The outer side of the timbers can remain curved.
Cut notches into the 42" timbers for the lap joints. Set your radial arm saw to 1-1/4" deep (almost half the thickness of the timber). Make two pencil marks on each end of the timbers -- one 3" from the end and the other 6-1/4" from the end. In between those two marks is where the notch will be. Slice 1/4" wide increments into the notch area (creating little grooves). Then use a chisel to remove the slices of wood inside the notch area (Image 2).
On the 14" timbers you'll only be making a notch on one side, the unnotched side will be the doorway. Make two pencil marks on one end of the timbers -- one 3" from the end and the other 6-1/4" from the end (just like above). Then cut out the notches in the same manner as above.