I can't answer this question directly, because there are a lot of false premises behind it. LoA is a universal principle. You don't really use it, it's always there, it's always active. That's the reason why techniques aren't really important. Important is that you understand the principle behind them. You haven't used any technique to manifest most of the stuff that's in your life now, right?
There is no technique in and of itself that is effective. How effective something is always depends on how properly you use it and what you think the rest of the day. It's fine to visualise 10 minutes a day and it can be effective, but if you spend the rest of the day waiting for the manifestation to occur or worrying about the absence of the thing you want, you could have spent this 10 minutes better with taking a shower or something. You could take a shower and not visualise, but think the rest of the day the right thoughts and the thing you want could come quickly.

The only thing you have to do to attract something in your life that you want is focusing on it and be as happy as possible. That' really all that is to it. When you think about him calling you, it feels good and you are aligned with what you want. When you think how he haven't called yet, it feels not so good and you are attracting more of him not calling in that moment. All techniques just try to direct your focus on what you want.

What I meant by false premises in the beginning is this: You ask how to make your ex contact you. So you think your now reality is so real that you have to start from where you are and go to where you want to be. In a sense, that's right, because you can't get anywhere else, if you can't accept where you are. But the false premise is that your Now has anything to do with your next moment. Your starting point here is "we have no contact" and that's the focus behind that question and that's the reason why this question can't lead you to the solution - it's the opposite vibration. You don't have to make anyone do anything. The ex who isn't texting you in this moment isn't the same ex who didn't text you a minute ago. You can choose the version of him you want to experience and focus on that version. You don't need to aknowledge in any way how it is now. It's completely unimportant.

https://youtu.be/SWwk555zWow