The pallets were a mixture of free pallets and the top of the island was a heavy-duty pallet used to haul steel plate that was thick and heavy (free too).
I've broken heavy-duty end pieces apart and used a sledgehammer to butt them together and used Torx heads to secure. With a gap in the middle, I knew I had to fill it. I've sanded and stained the top, used cheap Harbor Freight sprayer, applied 3 coats and sealed it.
On the bottom side of the middle gap, I hammered in pieces some scrap pallet and cut down to fit tight and wood glued in but left a 1/8 gap from the surface to the top of scrap to lay tile and grout.
The tile was a 12x12 square wall pavement I cut pieces out of and just laid in the gap using tile spacers and grouted. I let dry and tile sealed it. For the bottom I just spray stained the rest of pallets, measured height and width to be almost bar height.
I started with the bottom pallet and screwed in caster wheels, then, I've just added stain pallets to the height I estimated from the church pew wood corner spindle I attached with L bracket on the backsides.
Before adding the top surface, I put together with iron pipe supports from Home Depot. I then screwed to the bottom pallets first then put a heavy top on and screwed everything together. I went around to both ends of the table and trimmed off overhanging pieces and brushed stained ends.