DIY washbasins, what accessories do we need?

Yes well, if nothing is included with the sink, of course you still need the appropriate drain fitting. Siphon is also a combo, it includes all sorts of pipes and seals.

The drain fitting is usually included with the purchase of the faucet from reputable manufacturers, as well as the hoses/pipes for connecting to the angle valves. Then you also need a siphon. These are also generally available with all necessary parts. But. There can still be other parts required. For example, longer drainpipes than those that come standard.

Just an idea, depending on the available space. Have a 40mm multiplex board cut at the sawmill, sand the edges a bit and then clear varnish or wax. Attach one side to the wall with a strip and on the other side a stylish metal runner (buy online or a local locksmith for little money). Place 1-2 sinks on top of it. Under this board the wide Godmorgen cabinet from Ikea. It’s all easy to do yourself (I'm not a real craftsman), inexpensive and looks really chic. Bathroom furniture is often boring and expensive.......

It was the same issue for us. The general contractor had nothing decent in their program - we found what we needed at IKEA.

The washbasins are from Laufen, or the small one from Amazon, and the faucets are from Grohe - however, only the expensive product included a drain valve.

We had the countertops cut to size and bought them specifically for washbasins online.

Super stylish and definitely easy to make, nice pictures.
I looked at various oak boards, all of them at exorbitant prices. You just have to browse a bit or free yourself from constraints and new ideas start to flow. As I said, my favorite for kitchen counters, long boards in bathrooms, etc. is 40mm multiplex, which is really cheap.

where did you buy the tiles online? Had any good experiences?