- Lots of reading, both extensive and intensive. Find sources of comprehensible input: sentences that you understand 60-80%, and will help you infer the rest by context. You will need lots of these. For instance twitter accounts in Korean, newspapers, etc.
- Watch shows with subs in your L1, or watch them 2 times: first time in L1, right after in L2.
- Use spaced repetition, but creating your on cards (active study vs passive study). Sentences better than words, bring context.
- Do some writing. Perhaps a journal, or something about your job / field of expertise. Notice the gaps (things you want to say but don't know how). Get it reviewed by a native.
- Have regular 1:1 sessions with a tutor / teacher, eg. on Italki.
If it is important to you, it is worth to spend a some money on it IMO.
Good luck!
What I am trying to say that if you are very serious about learning Korean you should research opportunities that will allow you to spend some time in Korea. It all depends on your current position/finances, but it may be easier than you think. There are many scholarships offered to language students that basically cover most of your living expenses. I encourage you to check them out. During my time as a student in Taiwan I've met people of all different backgrounds. Students, senior managers, people with Taiwanese SOs, etc. If you can only do it for a month -- do it. I think going to the country that speaks the language you're learning is the only way to actually improve.
---
So far I'm liking it.
Maybe Korean Associations, travel, find an online chat buddy you can facetime if nobody locally.
Weird side story, when I lived in Mongolia many people would pay me not to learn English but just to have a conversation with a native english speaker. They were motivated to not just learn but also to get better.
One recommendation has been to spend more time writing in Korean (like blogging) to better put my thoughts into the language and I guess in theory, means I would become quicker in conversation.