Weird artifacts when two models are overlapped

Hi everyone! This is my first post here.
I’m making a Minecraft Skin Editor using Three.js (I’m a newbie). I have weird artifacts that comes from the texture when I overlap my two models (there’s a 8x8x8 cube that represents the skin’s head, and a 8.25x8.25x8.25 cube that is the “outer layer” of the skin. The 2 cubes qre overlapping each other).
I’m using the MeshStandardMaterial material for both parts. Here’s a screenshot below with the artifacts visible.