There’s several free load boards out there. The problem you’re going to run into is getting a owner operator, or even a carrier with a bad attitude, and/or a poor work ethic. Unfortunately there’s an abundance of them out there. Many of the shippers, and brokers that I help move freight for prefer to not post their shipments on load boards because they’ve had multiple bad experiences with owner operators/carriers.
if you’re going to post your own loads, partials, whatever, I’d recommend using a load board that you’ll have to pay a monthly fee to be on. Some load boards will help you in the event you run across a bad owner op/carrier. The free load boards, they’re not going to help you.
Most owner operators will look at a brokers, or shippers credit rating, and experience when determining to call them about a posted load/partial. If they’re not very experienced it'll show and the good owner operators/carriers will more than likely avoid that particular broker or shipper. One thing you can do to counter that issue is to offer them payment on Delivery, or even payment on pick up until you build up a reputation for being a upstanding shipper/broker. That can take time.
Most Owner Operators/Carriers don’t even realize it but brokers/shippers can also report them to load boards if they give bad service, or pull something unethical. When you’re checking out load boards ask them if you'll be able to look up carriers in their data base to see if a broker, or shipper has had anything negative to say about working with them.