Place flour sack towel over a glass bowl. The towel I used is 28x29 inches. Please note that it is not a regular kitchen towel but a muslin type fabric as seen in the pictures and video.
If you want to add salt to yogurt, this is the time to do it. I skip the salt personally. Scoop or pour yogurt right in the middle of the flour sack or cheesecloth. If using cheesecloth, you'll need to use at least 4 layers.
Grab the 4 sides of the flour sack, tie them in knots and hang the flour sack with yogurt in it for about 1 hour over a glass container so whey can strain out of the yogurt. You'll see a greenish liquid strain through the cloth. If you see a white liquid straining, it means the cloth you're using is too thin, you'll need to double or triple the layers.
After about an hour or so of straining this way (yogurt's own weight helps strain really fast), you can check consistency and it will be really close to Greek yogurt at this point. You can pour part or all of it in a container and refrigerate for your own Greek yogurt uses.
If you're looking to get labneh, spreadable cheese like or salcë kosi, then don't untie the knots of the flour sack, rotate the flour sack around the knot and place it over a colander being supported by a glass container. The volume of the flour sack with yogurt should have gone down a lot during the hour it was straining so it should fit now over the colander or strainer.
Place the whole glass container/colanger and flour sack with yogurt in the refrigerator overnight. The yogurt will strain into a soft cheese like substance and the next morning you can remove from flour sack and place it in its own container for use as you see fit:)). Enjoy!
Notes
Note - since the uses of strained yogurt vary so much, so will the amount of servings depending on what you're using it for.
The nutrition values for strained yogurt are a bit hard to calculate, so this is just an estimate.
Straining time will depend on how much yogurt you're straining at a time, type of fabric you're using to strain and if you hang it initially or just straight place over colander. Since this is not a fixed formula, do a little check every few hours to check on consistency the first time you're making strained yogurt. You'll fine tune it to your liking:).
Always prepare more strained yogurt than you need for your recipe, it's better to have extra than come up short since it takes time to strain.