This is my latest work, bathroom makeover. It is a wide sink (60cm x 40cm) with lots of space underneath.
The total cost is under 70 euros
www.instructables.com/id/concrete-sink-123D/

Step 1: Clean Area First

First i removed the old furniture and sink and then cleaned all the area from any residue (glue, dust, etc)
Once area was cleaned i did all measurements and calculations for all the ingredients and tools that i would need.

Step 2: Ytong and Glue

I started the construction with ytong blocks. In order for them to stand and tick together i used ytong adhesive. The blocks i used are 60x25x5 at the base and some for the vetical panels, 60x25x7.5 at each side and 60x25x15 on the top. https://www.instructables.com/id/concrete-sink-123D/

Step 3:

this is a fortified with cement area for the faucet

Step 4:

The entire surface has 2cm concrete fortified with iron net. In the sink i left a hole for the drain.
It takes more or less one day to get completely dry.

Step 5:

When the concrete was dry i smoothed all the surfaces and insisted on the edges

Step 6: Cover All Surface With White Concrete

I used white concrete mixed with resin for more strength and tolerance to cover the entire constuction. It dries fast, and once dry again i smoothed it all.

Step 7: Resin Concrete

I removed all dust very well, insisted on the details and i used matte sealer for water protection. https://www.instructables.com/id/concrete-sink-123D/