Combine the apricots with the sugar and let them macerate for at least an hour (overnight is even better).
When you're ready to cook, prepare a boiling water bath canner and enough jars to hold around 5 half pints of product.
Pour the macerated fruit into a low, wide, non-reactive pan and set it over high heat. Add the red chili flakes.
Bring the fruit to a boil and cook, stirring occasionally at the start of cooking, and nearly constantly towards the end.
The cooking process will take anywhere from 15 to 30 minutes, depending on the width of your pan, the water content in the fruit, and the heat output of your stove.
You're looking for the jam to get glossy, for thick layers to form on the walls of the pan, and for the jam to sheet nicely off your spoon or spatula. When it does all that, it will be done.
When the jam is thick enough for you, remove the pan from the heat and funnel the jam into your prepared jars.
Wipe the rims, apply the lids and rings, and process in a boiling water bath canner for 10 minutes. When the time is up, remove the jars from the canner and set them on a folded kitchen towel to cool. When the jars are cool enough to handle, test the seals. Sealed jars are shelf stable for a year or more. Unsealed jars should be refrigerated and used promptly.