This stand holds a quart bag open while you fill it.
Fold the top of the bag over about an inch to hold the bag on there.
This thing works pretty well, and it's a real convenience when you need to bag a lot of meal sized portions, particularly liquids like soup.
I use it here on a large pot of chicken cacciatore. Another photo shows it holding a quart of plain water. These standard size (Walmart) quart bags actually hold about 5 cups.
The stand is kinda thick and bulky, but it is stable and strong. I couldn't figure out how to make it fold for storage, but it disassembles easily and the 5 parts fit in a quart bag.
My attempts to design one that would hold both quart and gallon bags were not successful. I may get the urge to do one for gallon bags, but I don't use a lot of them and doubt it's worth the trouble. This one might simply be scaled up to gallon-size, but I haven't tried that.
[Update: I frequently use the "Sous Vide" cooking method and discovered that instead of expensive vacuum bagging, the plain gallon zipper bags can often be used. So I made the gallon version of this bag filler. https://www.thingiverse.com/thing:1960297]
The "top" took about 56 minutes, 28 grams, and a single "foot" needed about 28 minutes 14 grams ABS. I recall needing 2 prints to get all the parts printed on a 5x5 Afinia build plate.
The printed legs may be a very tight fit. Use some sandpaper on both ends of the legs to get a smooth sliding fit. It's only a print, and something will break if it is stressed too much. There's no need for things to be tight. Gravity holds it together.
Metric files provided.