This is one of my favorite activities for students who share a common language other than English. This activity falls under the acronym of KISS (keep it super simple). The teacher won’t have to do much, apart from weaving things around (I’m just stating the obvious).
Ask your students to look through language that they have seen in class over the last four weeks or so. The source can be the coursebook, handouts or off-the-cuff language that you have written on the board. This should be challenging words and expressions (no need to choose the word “table” at an Elementary level or “lazy” at an Advanced level). Ask them to spend about 5 to 8 minutes to look for a handful and translate them into L1. It works even better if they can provide a full sentence, which they can get from a dictionary or they can make up their own. For instance, if the target word is “snore/snoring”, they can translate it as -let’s say- “schnarchen” if their L1 is German, or, better still, they can come up with something like “Vom eigenen Schnarchen aufgewacht” (“awakened by his own snoring”). Then, have the students, one at a time, read their translated words or sentences to challenge the classmates.
If you want to spice this up a bit, ask them to write each individual item on a small piece of paper (L1 on one side and L2 on the other). Collect the pieces of paper. Set up groups of about 4-6 students to a group. Distribute the pieces of paper evenly. Ask the groups to lay the papers L1 side up. Give them 5 minutes to devise, in their groups, a way to play a word challenge game based on translating those items. Then, they can start playing the game. Encourage them to swap papers with other groups. Make this last for at least 10 minutes. Collect the pieces of papers and focus on 8-10 interesting ones. Finally, ask the groups how they ran the game. Which group do they think had the most exciting rules?
Keep what you believe the best pieces of paper are in terms of interesting or useful words and expressions or clear examples and use them again in the future. The students can write new words and expressions and you can give them the old ones as well.
Maximum student output, cognitively engaging activity, useful vocabulary revision, zero teacher preparation time.