Should the flag of the Kingdom of Saudi Arabia be treated like the flags of other countries during design, and is it permissible to place anything above it or display incomplete words from it, such as "ول الله" (and God) or "لا إله إلا" (there is no god but) if unintended?

If the design does not lead to the denigration of the word of Tawhid written on the flag, and if shortening the phrase does not result in a corrupt meaning, then there is no impediment to creating that design. A corrupt meaning would be, for example, limiting it to writing "لا إله" (there is no god), as this opens the door to placing the name of a false god other than Allah.