A Flexi Case is two materials working together. The case is rigid PLA, open on both faces. The cover is a flat sheet of TPU that folds around the side of the case and closes both faces at once. A rib under the cover presses into a narrow groove along each rim and holds the cover in place, with no hinges and no hardware.
Set the outer size, then divide the inside into a grid of columns and rows, with proportions of your own. The corners of the compartments and the edges of the dividers are rounded, so small things slide out easily. The strap that joins the lids is longer than the side of the case and forms a loop to hang it. Flush with one end, as on the OneBlade case, the loop also lets the case stand upright. Move it along the side, or add a second strap at the other end, as on a passport cover. You can also close the bottom of the case: the cover then has a single lid, and the strap ends in a round tab that snaps under the bottom.
Print the case in PLA, standing on one of its open faces, with the seam in the small groove on one end. Print the cover in TPU, flat on the bed, with walls only and no infill: the hollow rib gives a little as it enters the groove and grips once it is in. The 3MF puts the case on filament 1 and the cover on filament 2. Patrons from the Initiated tier up can add a surface texture to the long sides and leave the engraved seal off.