You might recall the scam of 2016 when it was uncovered that when people are buying dried oregano in packets, it might be anything but that. Dry and dusty and flavourless - and that's the case even if it were real oregano being sold. Far better to grow - and dry - your own.
Most herbs I prefer to use fresh but dried oregano is a staple in my pantry, used to lift many dishes with its unique flavour. Summer is the time to be drying it for the year. Not only because it is good drying weather but because oregano goes nuts in the garden in hot weather, extending long stems with flowering spikes. Bees will be attracted to the flowers so be careful when you harvest.
Cut the stems as far down as you can. Gather a bunch and give it a good rinse to get rid of any residual dust on it or little insects. Pat dry with a clean tea towel and then tie it up loosely but securely. Hang it either inside in an airy space; or outside but OUT OF DIRECT SUNLIGHT.
Depending on the conditions, it may take 2-3 days to dry to a crisp. At this stage, take it down and rub each stalk free of its dried leaves and flowers over a tray or large sheet of paper. If it is properly dry this is easy to do. It must be at this stage otherwise it will quickly go mouldy in storage.
I then transfer the dried oregano to either a ziplock bag or jar with a tight lid and store in a cool, dry, dark part of the pantry or spice rack. (The stems can go to the compost bin).
Drying chillies from your garden is even easier. You could put them in a dehydrator, but they make a decorative statement in your kitchen if you air-dry them. This is done by stringing them up. Forget fiddly knots around each one but dig out a sharp sewing needle and some thin thread and get to work. After knotting one end of the thread. sew through the green stem end of each chilli. They will overlap but do give them some space by not forcing them down too tightly to dry more thoroughly.
Complete dryness might take several weeks, especially if you leave them indoors (out of direct sunlight). You can speed it up a bit if they hang in a sheltered spot outside. Once completely dry to the point of being crispy, you can take them down and store in a container; or, for chilli flakes, put them in a coffee grinder, preferably one that doesn't get used for coffee! Or you can simply leave the dried chillies hanging and take each one off as needed.