No, it's not OK. It's a flat out lie, and if some potential employer makes the entirely reasonable request to see evidence that you were paid for your work, you're going to get caught out.
Indeed, the main reason gaps in your employment history look bad is because they're lies of omission. So long as you can put something down that you can back up - even if it's a year-long backpacking holiday - at least a future employer can safely conclude that you didn't have a string of bad jobs from which you got the sack, spend the time in jail, or worse.
Obviously, you still want to be selling the positives though, so perhaps try retconning that period into one where you made a dedicated push towards bridging the gap between the skills you graduated with and what was needed for you to get paid work. So long as you can produce quality work and come across as confident now, I doubt anyone's going to question that version of events, but it certainly sounds a lot better than the first version you gave us.