Story,
1kilo Seville oranges plus one lemon, 4 pints water, 2 kilos sugar-according to the blessed Delia, utterly foolproof.
Measure water first, easy to get distracted, then I'd defrost, halve, squeeze the oranges, add squeezing to water. Put muslin on plate, I use a baby muslin, use nails to scratch inner skin and pulp onto muslin, slice skin and pith, tie up muslin, dump muslin and skin in pan with water and juice.
Simmer until the skin is soft, for frozen oranges, probably an hour, otherwise 2 hours. At this point, you can cover with cling film and leave overnight, or continue, absolutely no reason to wait unless it's convenient.
Then wash hands, grab the muslin, and squeeze, and squadge, into the liquid, I reckon for about 10 minutes, you'll get loads of thick goo out, the more the better.
Warm the liquid until just simmering, add 2 kilos of sugar, no need to warm, stir until dissolved, then boil hard for 15 mins.
Leave 15 mins then pot up. I don't bother with sterilising pots, I run them and lids through the dishwasher at high temperature.
I have a plastic jam funnel, use a folded kitchen towel to hold pot, fill, and have a dampened towel to wipe any spills.
Sounds complicated, but once you get into the groove it's easy, fourth batch in process...