You know how to produce all English sounds, but your ear can't discern some sounds, like L×R for Japanese. Indians may be troubled with pairs V×W and θ×ð.
1. Identify the confusing sound pairs and difficult sound combinations.
2. Pronounce aloud those words and listen to your utterance.
3. Practice daily until you are no longer confused with the sound pairs.
4. Practice difficult sound combinations until it is effortless to produce.