Ye Mo used four days and set up a space lock formation around the seal flag. This was level nine peak. This was the limit of his formation due to skills and materials.
He knew that if he didn't do it right, the seal flag might explode instead. If it did, the power would be huge. If he couldn't get into Golden Page World at the right time, he might be seriously injured even with his god state body refinement.
He was going to make the seal flag automatically hide into space and then get blocked by his space lock formation.
The most important thing wasn't to stop the seal flag but dragging it into his Golden Page World. Otherwise, it was impossible to keep all the immortal crystals in the seal flag. If the seal flag went into his Golden Page World, it would be completely under his control.