The stool is light and can be dismounted into small parts very easily. It has the minimum footprint to support the ischium (the 2 bumps of the pelvis on which the weight of the upper body rests) comfortable. The surface has slight ergonomic indentation. The surface has an inclination of 10° to match the angle of the thigh when the knee rest on the floor.
It looks very small and creates doubt if one can sit on it, but it is surprisingly comfortable.
As legs I have used thin aluminum tubes of about 8.5 mm diameter. The length of the front leg must be a little bit shorter (7mm) because of the 10° slant. There are covers for the base of the legs to prevent the floor from damage.
To print
Additional
The FreeCAD source isn't fully parametric. The main dimensions are in a separate spreadsheet but front leg mount and the holes for the legs are manually positioned. The angle of the legs has made it difficult for me to make it all parametric.
The author marked this model as their own original creation.