To construct a whole ceremony, you can’t just make it up on the spot. That is not a ceremony. A ceremony has a past. A ceremony is done a certain way because that’s the way it’s always been done. In short, to build a ceremony, you have to create a ritual first. Then, the ritual can be constructed into a bigger, more lavish ceremony.
This kanji also means equation for some reason too. Just think of a ceremony that involves doing math and coming up with equations. How strange would that be? Pretend you're at this ceremony.
So, you’re at a ritual. Think of the most ridiculous ceremony you can think of. Give it a shot – I’ll let you come up with the ridiculousness this time (it’s good practice). When you think of your mnemonic, make sure to imagine it with a Sheikh (an Arabic leader). Have the sheikh do something ridiculous to help you to think of this sheikh (しき) and then remember this on’yomi.
Currently there are no similar looking kanji which exist in the WaniKani learning system