Did I miss the part where the title was answered?
The article mentions some building blocks like microlearning, explains how researchers test people with, for example, fictional words and shapes to avoid that you draw on prior knowledge, states that "experts make a case for human instruction" (but not which case or how that human instruction should be shaped or structured), and shares shards of how well the author did on the different tests. There's a lot of links, which is nice, so I can dive deeper into the things mentioned (I've read a bit about 'statistical learning' and plan to read the linked paper on microlearning which is new to me), but I am not a step further in what (combination of) method(s) is the "best way" up learn a new language. Did I overlook it or fail to put some pieces together?
Edit: that microlearning paper (10.22034/meb.2022.355659.1066) is a waste of time if you've read the submission whence it was linked and know about spaced repetition. The paper makes a case that society has become more fast-paced since Charles Babbage made the difference engine in the 1800s and so microlearning can help us by breaking down lessons to fit into our day, lowers costs per lesson etc., but might also fragment the learning (and other obvious pros and cons). The most interesting part was a forgetting curve cited from another paper