Which technique should you consider using throughout the Selenium script if there is neither frame id nor frame name?

If neither frame name nor frame id is available, then we can use frame by index.

Let’s say, that there are 3 frames in a web page and if none of them have frame name and frame id, then we can still select those frames by using frame (zero-based) index attribute. Each frame will have an index number. The first frame would be at index 0, the second at index 1 and the third at index 2. Once the frame has been selected, all subsequent calls on the WebDriver interface will be made to that frame.

Example:

driver.switchTo().frame(1);