Council: it is desirable to take boards for production of backs with a stock, so you will have an insurance in case it will not be possible to cut from the first correctly details for their normal joining.
Collect a frame of future bench. At you it has to turn out approximately as on a photo. Do not forget about crossing points which will make a frame more rigid and steadier.
Council: that gaps between boards were uniform, it is possible to use speyser for laying of a ceramic tile.
Council: it is best of all to begin a covering of seats with the length of a board which will pass along a forward edge of the central section of our bench.
Council: it is best of all to begin assembly of a frame with back (longest) beams.
Sides of boards can be polished that they were slightly rounded. Record all boards corrosion-proof screws.