I only bring this up, because the team is paying particular attention to their block models. Just in case.
- Slabs, Anvils and Fences have a solid black bottom face.
- Torches ( normal, redstone, and those on Comparators & Repeaters ), the 3 Chests, mob Heads, Iron Bars, Glass Panes the End Portal, and Hopper have a fully-lit bottom face.
- The Slime Block has a dimly-lit bottom face.
- All other blocks are rendered without a bottom face. Including full blocks, but also things like signs, flowerpots, etc.
- Additionally, Doors render their sides when against a solid block, but not their bottom when above a solid block.
- Also additionally, the underside of the top half of an Anvil is black, in addition to the very bottom being black.