Hope you find my tutorial useful :)
If you have any questions about making your garter belt, feel free to ask! Also, since English is not my native language, feel free to correct my mistakes.
We shall start with creating a pattern for the garter belt.
I will show the construction of the pattern using as an example waist that measures 60 cm. If your waist is wider, you should draw an appropriately bigger pattern. You can also make your pattern longer if you want.
Draw a line measuring 1/4 of your waist circumference minus 0.5 cm (for me this line will be 14.5 cm), next, 2 cm space, and next, another line measuring 1/4 of waist circumference minus 0.5 cm.
Now your pattern's waist circumference is a bit smaller than your real waist circumeference. It is because you will be adding a fastening that will bring the missing centimeters back.
Determine the positions of garters.
The distances between the places where you will attach your garters should be fairly equal. In my pattern, the distance between the front garters is 6.5 cm; between the front and the side there is 6 cm; another 6 cm between the side and back; 6.5 cm between the back garters.