Place angle brackets on the wall where you want the free-standing shelves to go.
To make the shelf, you take a skin and make the bottom of the shelf, a piece of 5/8" plywood is added, then add a spacer made out of luan that is the same thickness as the angle bracket and a top skin goes on top.
Note: Angle iron brackets are made of steel that is 3/16" thick.
Glue 5/8" plywood to the bottom skin, and then glue the skin trim to the front and sides of the shelf to cover the wood sandwich core. Use pin nails to help hold the trim in place until the glue dries (Image 1).
Use a bead of paneling or construction adhesive glue on top of the plywood and spread it with a trowel (Image 2). This is the base for the next layer, which is the luan.
Put the luan on after the glue has been spread and hold it with pin nails. The luan is approximately half the width of the shelf -- allowing room to slide onto the angle bracket.
Repeat the application of the construction adhesive to this layer, then put the top skin in place and nail it. This is actually the bottom of the shelf and won't be seen, so regular nails can be used, securing the whole unit.
After the planks are glued, drill pilot holes near the end of the board for the T-bolts that will line up with holes that will be drilled into the angle iron.
Using a slightly larger drill, countersink the hole to receive the head of the T-bolt, repeat this process on the other side of the shelf for the T-nut. The T-nut has sharp points that are tapped into the wood and they stay there for good.
Once the shelf is glued together, use clamps to hold everything in place until the glue dries.
You can assemble the shelves while the glue continues to dry.
Slide the shelf onto the angle bracket and use the pilot holes to drill through the angle iron where the T-bolts will go (Image 1), clamping the shelf to the angle iron.
Note: Use a sharp hardened alloy bit when drilling through steel.
Grind off the end of the T-bolts so they do not stick above the shelf. Be sure to use cardboard to protect the wood (Image 2).