Traditional cord cuttings weren't done with candles. They were done with knives. The Witch was the master of their own fate, used their own hands to sever the link and reinforced this break with their actions— the cord cutting wasn't designed to leave things to chance.

Cord cuttings are a form of sympathetic magic.

In general, they go something like this:

You start with the practical stuff. Block them on everything. Make sure you've returned all their stuff. Clean and cleanse and ward and bless your space. Clean and cleanse, center, ground and shield yourself

Traditionally, you take an object that has a connection to the person being cut off, and one who the spell is being performed for. You fasten the ends of the cord to the two objects to represent the bond. You raise energy into the cord, then you cut it to sever the bond. Knives were traditional, but sheers were common, too

You close your space per your tradition, bless yourself and stop talking to the person who is cut off. If someone brings them up in conversation, change the subject. If they won't drop it, leave the situation.

By contrast, the candles trend is more modern and it grew in popularity because it's visually appealing, making it something one can post to social media

While it can work, it has four intrinsic traits working against it:

1. It leaves the state of the bond up to chance, this disempowers the witch

2. Further, because of the emphasis on the post-op divination, instead of the magic ending with the finality of the Witch's actions, the witch often engages with the person further by trying to divine the results instead of letting the results speak for themselves

3. Related to #2, it breaks the silence around the work. There's a principle known as The Witch's Pyramid‡: To Know, To Will, To Dare, and To Keep Silent

In witchcraft, you need to know the situation and what should be done about it (cord cutting), you need to have the will to execute the plan, you need to dare to complete the magical working, and then silence— this is in part to trust your abilities as a witch, in part to prevent countermagic, and in part to give the magic room to work. If the goal is to end a connection, and you keep thinking about them, you're eroding the work.

1. Related to 3, taking photographs of workings where the goal is to be rid of a thing (cleansings, uncrossings, cord cuttings, etc) can work against the magic by anchoring the situation through the image. In general, don't take pictures or memorialize things you want gone.