To hollow cosplay 3D models while maintaining good bed adhesion, create or modify the model with a flat, solid base (for build plate contact) and use slicer software to hollow the upper parts while retaining that base.
The solid base increases adhesion via more surface area (reducing warping), and slicers like Cura or PrusaSlicer let you set a 2–3mm wall thickness—balancing durability for cosplay (needs sturdiness) with light weight (easy to wear).
If your model lacks a solid base, use free tools like Meshmixer to add one before slicing. This ensures adhesion without compromising the hollow design.