A stack of realistic slices of toasted white bread, count is stackable via geometry nodes modifier, combining textures and procedual materials. with moldy spots and hairs.

Including "Staking" geometry nodes modifier.

The mold is generated via a geometry nodes modifier, which influences the material and hair particle system. Fully procedual mold, adjust it for your needs, controlling scale, detail, distortion, strength, density. In addtion you can adjust the stacked count if slices via a geometry nodes modifier too.

Note: Works best with Blender version 4.4+, but works with Blender versions tested down to 3.6.

Materials:
procedual, textured, hair particles

Size, real world size of a slice of american sandwich toast:
starting from ~ 11 x 11 x 1.2 cm, one slice