The skeleton frame design minimizes filament usage and allows the trays to be printed quickly using spiral vase mode. The frames flex some but the bottom flanges prevent the jars from falling out. The spiral ends are designed to fuse with the adjoining walls to add extra rigidity.
The trays are available in 2x2, 3x3, 4x4 grids or a round 7 in a number of different jar diameter sizes. See the download folders for options.
Setting Bottom Layers to zero saves a little time and filament by not filling in the center walls. In Cura the first layer will look like this:
In Cura:
Enable Spiralize Outer Contour under the Special Modes category.
I found a bug with the Smooth Sprialized Contours setting so disable that.
In Prusa Slicer, enable Spiral Vase in the Vertical Shells section on the Print Settings tab.
If the frame flex is too much, a brim could be added in selective locations to tie the walls together better without using too much extra filament or print time.
Other Notes:
The 22mm diameter 4x4 tray will fit these Sterilite baskets 3 across and stacked 2 high.