Purchase as many ready-to-assemble cabinet units as necessary to stretch across your room. Remember that you will need room at one end or the other to move around the divider.
Assemble each unit, but skip the backs and the doors. Place one of the loose backs onto one piece of plywood and trace around it. Do the same with the rest of the plywood pieces and cut out the new unit backs using a table saw.
Attach the new backs the cabinet units with approximately 4 finishing nails along each edge. Cover the nail heads with wood putty, let it dry and sand it to a smooth finish. Paint the cabinet units as you desire and let them dry completely.
Place the units flat on the ground, with every other unit face down. Align the sides of the units and attach them with flathead screws sunk along each side on the interior.
Paint the unit doors separately and reattach them once they are dry. Hide the screws with wood putty just as you did the nails, then touch up the paint and let it dry before positioning the divider in your room. To permanently secure the divider, attach it to one wall with sturdy angle brackets.