Last time ended with a plan: before choosing a style for the new glass arc over the Iron Island chest ring, bring the item elevator all the way up to meet it. The title card again reads "Iron Island Item Elevator Design." The idea is to style the arc "based on the item elevator's already existing design."
Up the elevator pattern
There's a new sign at the base: "Incomplete... You may want to turn around and try again." Basket isn't sure who put it there. Then it's supply time: trapdoors and four kinds of glass, with glass and sand both running low.
The elevator's pattern repeats in layers of glass, trapdoors and blue bands, and Basket builds it up layer by layer, keeping the lower elevator running as it is. A few blocks go in wrong and come back out. Near the top Basket runs out of blocks, restocks, and gets back up with ender pearls. The first throw misses entirely.
Fake water at the top
The pattern reaches the arc. Following it one more layer would make a blue band, right where the water will be, and Basket likes that. Water from the top will flow one way and carry the items, so blue blocks with torches stand in as "fake water" pointing the other ways for now. A ladder goes up the far side, so there's no more ender pearling to get up there.
The sorter in the ring below still isn't hooked up. Basket is waiting for 1.12, which is "supposedly" coming out tomorrow.
Three tries at the arc
First try: flip the elevator's bands so light blue and white rings run down the arc. It doesn't work. The blocks don't behave the same way sideways, and the trapdoors can't follow. "I'm pretty sure I don't like this pattern."
Second try: a band of iron blocks along the top, white glass below, and real water poured down from the top to see the full effect. From the ground, "you can't really tell that the iron is even there." The lights don't help either.
Third try: white stained glass the whole way, with the lights only in the top middle and the water running underneath. "So far better than our other plans," Basket says, but it still needs something. A viewer asks about blue glass panes under the water, and Basket worries items might fall through or get stuck.
Something at the center
Another viewer says it needs "a little something to bridge from the center." That gives Basket an idea: a separate structure on the top middle, which would also hide some lapis blocks up there. Dark prismarine could tie in with the prismarine in the mob farms below. The plan is a 5x5x5 cube with 3x3 pieces sticking out the sides where the water comes out.
Dark prismarine is pricey to make just for a test, so Basket borrows some from a guardian farm whose sign says to take anything. The blocks can go back if the idea doesn't work.
The borrowed blocks run out partway through, and Basket fills in with other blocks to finish the shape. Seen from below, it looks too small. Maybe 7x7, or a flattened donut, a torus, the same height but reaching out a block or two farther. A viewer thinks the flattened donut could work.
Squid for ink
A bigger shape means a lot more dark prismarine, and that takes ink sacs. Basket drinks water breathing and goes after squid in the water around the island with a looting sword. "This is my squid farm." By the end there are "almost three stacks."
The plan from here: a torus up top to bridge the elevator and whatever the arc ends up looking like, then hook the item elevator up so items run down into the sorter. "But that will be next stream." The video ends on the credits, with no gameplay after them.