Hi there,
Thank you for your inquiry and we sincerely apologize for any inconvenience.
There are no secrets in opening the mini cubes. We actually found out that the previous mini cube batches had loose lids so we had requested from the manufacturer to tighten these lids, resulting in the lids being too tight. We are currently working on this. In the meantime, you can use an engraving/hobby cutting knife to go in the slit between the lid and the bottom portion of the ink and twist a bit to create a bigger opening for an easier way to open up the inks.
I hope this helps. Please feel free to message us again if you have other questions and we'll be glad to assist.