I've updated my calibration strip idea to test the entire bed. You're aiming for all of the strips to be started and stopped without an issue. Also, the twin parallel boxes allow you to quickly see which corner needs to be adjusted using bed level correction.
I've had great success using this, I thought it more important to see how it performed by starting and stopping small strips rather than printing a big square in each corner. This way you can really dial in. I can now utilise the whole bed for printing multiple small parts, as it will now start a small print anywhere on the bed without issue.