Measure using a digital kitchen scale. There aren’t proper volume equivalents for some of the ingredients.
Place all ingredients in a large bowl, and whisk to combine well. The pectin should be used without the calcium packet. Store in an airtight container at room temperature until ready to use.
The recipe can be halved or used in multiples easily. Just be sure to whisk fully in a large enough container.
Use of lower quality ingredients than those to which I have linked in this post (including the xanthan gum and pectin!) will result in a markedly lower quality product, one that does not behave at all like mine. Proceed at your own risk.