Start by washing your oranges as usual and let them dry while you sanitize the jars for the cheong. You can sanitize the jars by placing them upside down in a pan of boiling water and letting them completely dry and cool on a rack. Or you can sanitize them by spraying/wiping the insides with alcohol. Make sure to sanitize both the jars and any other parts of it such as the seals or lids.
Split the oranges into two batches and start peeling half of them. Divide the peeled oranges into two groups. Cut the oranges of one group into small bits, splitting the wedges and set aside. Then, place the remaining peeled oranges into a blender or food processor and blend until all liquid.
Place a bowl on a scale and add the cut oranges and juice to weigh it out. Whatever the number is, add the exact same amount of sugar. Lightly mix together, cover with a plastic wrap, and set aside for now.
Clean the remaining peeled oranges by removing the pedicel (green star shaped part) and rubbing them with baking soda and rinsing with warm water. Thoroughly dry off with a paper towel.
Thinly cut and discard the ends then cut the oranges into thin slices, approximately 5mm or ¼ inches. Similarly, weigh out the total of the oranges. Weigh out the same amount of sugar, but only add ¾ of this number to the oranges and weigh out the remaining ¼ in a different bowl.
Mix the orange slices with the sugar and start adding it into your clean and cool jars. Once finished adding the slices, add the remaining sugar as a layer on top and seal the jar.
Now back to the first batch. The syrup should be slightly thicker now, but you can let it sit in the bowl for a couple of hours until the sugar is mostly dissolved. Once dissolved, add it to the other clean jar.
Let both jars sit at room temperature until the sugar is fully melted. Depending on the weather or climate, this can take as little as a few hours and as long as a week, so just keep an eye on it.
Once ready, store the cheongs in the fridge. The first batch we made will be thicker than the one made with the slices, making it good for baking, tea, etc. The second batch will be runnier, making it good for adding to iced drinks or cocktails. Try to use it up within 2 weeks.