Istisna linguistically means: requesting to manufacture something. Manufacturing something: that is, a call to make it. Istisna idiomatically: that is, a person asking someone else for something that has not been made yet, to make it according to certain specifications, with materials from the manufacturer in return for a specific compensation. The manufacturer accepts that. Examples include:
1. If you go to a building contractor and ask him to build you a house. The building materials are supplied by the contractor. Then this is Istisna.
2. If you go to the tailor and ask him to make a dress for you. The cloth is supplied by the tailor. Then this is Istisna.

The evidence is from the Sunnah of the Prophet (Peace and blessings of God be upon him) as it came in Sahih al-Bukhari: On the authority of Abu Omar (May God be pleased with them): “The Prophet (Peace and blessings of God be upon him) made a ring of gold and made its stone inside his palm when he wears it. Then people make rings of gold. He (ascended) the pulpit and praised God and thanked him and said: I made it and I do not wear it. So, he rejected (left) it. So, the people rejected it. Then he (Peace and blessings of God be upon him) took a silver ring.”

1. The capital may be delivered in full upon contracting.
2. It requires delivering the capital (accelerating the price) upon contracting.
3. Determining the specifications of the thing to be manufactured in a precise way that prevents any conflict in it by mentioning the characteristics by which the price varies. In the assembly held for contracting, it must mention the type, gender, amount and required descriptions of the manufactured thing.
4. It is stipulated that the specified date for the manufacturing of the thing must be specified in order to prevent any conflict.

Yes, the penalty clause and a fine may be taken in return for the delay in the manufacture of the thing after it is agreed upon in the concluded contract. This is what was approved by the Islamic Fiqh Academy.

Yes, there is ignorance and deception considering that this sale is non-existent. But the Shariah permitted it for the sake of the great interest and benefit of Muslims. This is part of the tolerance of Sharia, as it permits some things that are forgiven.