as in alive and arrive
Below is a list of words that vary only by one having the sound /r/ and the other the sound /l/.
You can use this list to practise the sounds, or as a list of words to be careful in pronouncing.
/r/ is pronounced many different ways in various English-speaking countries and regions, so it is not particularly useful to ask students to base their pronunciation on what native speakers do with their mouths. As making a distinction is the most important thing, it is often better to exaggerate the differences between the two sounds. These descriptions are therefore meant to be useful for students rather than explanations of usual pronunciations.
/r/ is totally unlike /l/ for English speakers. In fact, some people pronounce it much more like /w/. The best way of making the distinction is try to move your tongue as little as possible when making the sound. (You can use your hand to help in the same way as suggested with /l/, but this time keeping your hand still. It can also help to start with your top teeth just touching the back of your bottom lip.)
View more information: https://www.englishclub.com/pronunciation/minimal-pairs-l-r.htm