No Face3 anymore, see THREE.Geometry will be removed from core with r125
Use Buffergeometry. Simple example in the Collection of examples from discourse.threejs.org
// … step 02: buildt custom geometries …
Another example RemoveTriangles
See also source code of the plane three.js/PlaneGeometry.js at d39d82999f0ac5cdd1b4eb9f4aba3f9626f32ab6 · mrdoob/three.js · GitHub