It depends on your fabrication technique and substrate. Generally the active material mass should be 10 mg or more for to avoid overestimation . Read this article for further insight " M. D. Stoller and R. S. Ruoff, Energy Environ. Sci., 2010, 3, 1294–1301."

There are many parameters to consider for fabricate device (two-electrode system).

It can be symmetric (two electrodes are same) or asymmetric device (two electrodes are different).

Moreover, you can make aqueous (liquid electrolyte) or solid-state (gel electrolyte) device. For aqueous device, you should take two electrodes, aqueous electrolyte, and separator to fabricate cell. you can check my paper for details.

Article Free-standing flexible MWCNTs bucky paper: Extremely stable ...

Complete solid-state device was constructed generally using PVA-LiClO4 gel electrolyte as separator between the two electrodes. Gel formation was performed as per standard procedure. The electrodes were coated with the gel and dried at certain temperature to remove water content. Both electrodes were placed on one another facing active surface. Uniform pressure (of 1 ton for 10 minutes) was applied normal to the plane of plates with the aim to increase surface adhesion which even enhance the mechanical strength of device. Further-more, certain pressure also helps for penetration of gel electrolyte inside the porous structure of electrodes which interface with the more active sites. Go through my publications. I've attached some of them.

Article V2O5 encapsulated MWCNTs in 2D surface architecture: Complet...

Article Large scale flexible solid state symmetric supercapacitor th...