Clip the assembled Cage onto the Shield to best fit and orientation for the battery. Use small drops of glue where the Cage touches the Shield to hold the Cage into position. Do Not Glue to the Crazyflie.
Install the battery. You may still need a small amount of doubleback tape underneath the battery but, much less and easier to remove than original.
The down pointing pillar on the central hub of the Cage is to help hold the battery in position. I use a folded piece of hobby foam sheet between the pillar and battery to add pressure onto the battery.