we chose a smocking technique that we liked and tried to make a 10 x 10 cm square. everything worked fine, except that we did not think about the demoulding process. in the end the form looked interesting, but the fabric was stuck inside the concrete. after trying with force, we saw that we would have to break the whole thing into a thousand pieces. so we came to the conclusion to burn the fabric, which did not work perfectly either, but it was interesting to try.
we tried to sew a pattern which should create a grid in the end. by hanging it upside down on a small structure, the concrete should have flown down to fill all the free spaces around the holes. unfortunately we were a little bit too optimistic about the size of 10 x 20 cm, so the concrete did not make its way down at all, before it could flow down it got hard and blocked the tubes. we even tried with a straw and an injection, but nothing worked. so the main problem was the size.