How to make a concrete bench
Part 4. Casting the concrete
Lay all the form pieces out on a flat work surface.
Step 4.1 Apply the release agent
Apply ample *release agent to all the form pieces on all sides with a paint brush.
Wipe off any excess with a rag.
Step 4.2 Half fill the bench form
Pack the bench form an inch or two up off the work surface so that you are able to get a hand under the ends. This is so you can lift an end up slightly and drop it multiple times in quick succession to vibrate and settle the concrete to help eliminate air pockets and make a smooth surface.
A little under half-fill the bench form with concrete and vibrate the form to settle the concrete. Do this by tamping and poking the concrete with a broad thin stick, say ⅛" (3mm) thick x 1½" (38mm) wide, also by using the rapid drop method as mentioned above, and also by tapping around the edge of the form with a hammer. The more vibrating the better.
Step 4.3 Place the reinforcing
Sit the reinforcing on top of the settled concrete, in the center of the bench form. Remember, the bench form is a little under half full at this stage.