I have project ideas that are 3x6 how can I do this with the crossfire
I wont say impossible, because technically it is not. However depending on the complexity and accuracy desired of the project it may be very difficult. That said, if you want to try and do it, you will have to pick a locating spot that you can set your origin at and have a several CAM set-ups to cut it. You will need to make sure you can accurately square your work piece to the gantry for each set-up and origin.
If you have several ideas that are all 3x6 foot, I would opt for a larger machine. If it is a 1 off project that has simple geometry give it a shot.