Grinder for plant substances

A method of manufacturing a grinder, comprising:

• manufacturing one of a first grinding section or a second grinding section of the grinder using a silicone material, wherein the first grinding section comprises a first surface, and the second grinding section comprises a second surface and a sidewall extending from the second surface, an edge of the sidewall is configured to abut the first grinding section to form a gap between the first surface and the second surface, at least one of the first surface or the second surface includes bumps that extend into, but not across, the gap formed by abutment of the sidewall against the first grinding section to encourage rolling friction between a substance and the bumps to grind the substance;
• and
• manufacturing another of the first grinding section or the second grinding section of the grinder using the silicone material or a metallic material.