Step 1 Predrill, then, using 45mm wood screws, attach formwork sides to formwork back and base with joints flush. Attach formwork front so top edge is 90mm down from top of sides. Predrill, then screw shutter between sides with back edge 140mm from front edge (this creates the rebate in block).
Step 2 Pour contents of 3 bags of concrete into wheelbarrow and slowly Photography Brent Wilson add water to make a workable mix. You do not want it too stiff as it will not flow into corners of formwork. To lessen final weight of blocks, you can add waste polystyrene blocks to sit inside concrete. Just make sure there is at least 50mm of concrete all around polystyrene. Continue mixing and adding concrete to fill up to level of bottom of rebate. Using a spade or a short length of timber, tap formwork to vibrate concrete so it settles properly and to eliminate excess air bubbles.
Step 3 Finish filling formwork to top. Use steel finishing trowel or float to smooth surface of rebate and top of block. Make sure concrete rebate finishes flush with underside of shutter. Let concrete set overnight, leaving formwork in place as long as possible after concrete has set and keeping block moist by hosing gently.
Step 4 Remove all screws from formwork and gently tap with a hammer to release it from block. Carefully remove formwork piece by piece (you will need to tip block over to remove base).
Step 5 Repeat Steps 1-4 to make a second concrete block.
Step 6 Find desired positions for concrete blocks, allowing for desired length of timber sleepers (here, ours measured 2100mm after they were cut), then spread a bed of 10mm blue metal for each block.
Step 7 Position both concrete blocks on blue metal, then check level.
Step 8 Using power saw, cut both seat pieces to desired length (here, 2100mm). Using electric planer, smooth upper surfaces of sleepers and chamfer edges to prevent splinters forming. Using belt sander, smooth all surfaces, starting with a coarse-grade sandpaper and finishing with a medium grade.
Step 9 Using power saw, cut three 50 x 50 x 360mm cleats with a 45° angle at each end.
Step 10 Put seat pieces together and position 1 cleat at each end and 1 in centre. Predrill, then, using 75mm wood screws, attach cleats to seat pieces. Finish with a coat of exterior furniture oil
Step 11 Position finished seat on rebates of concrete blocks.
Step 12 Add plants, then cover area around and under bench with blue metal.