To raise a flag in English is called "hoisting the flag". This phrase comes from the act of physically lifting or raising a flag using a rope or pole.

Here are some examples of how this phrase can be used in a sentence:

The soldiers hoisted the flag to signal the beginning of the parade.

The sailors hoisted the ship's flag as they set sail.

The children hoisted the school's flag at the start of the day.

In each of these sentences, the act of raising the flag is being described using the verb "hoist", which is used specifically to refer to the act of lifting or raising something using a rope or pole.