1. Explain it simply
A verb or time phrase + 的时候 means 'when...', and the main clause follows.
我睡觉的时候 means 'when I sleep'.
的时候 comes AFTER the verb or time phrase, not before.
2. Show examples
我睡觉的时候，妈妈在做饭。
Wǒ shuìjiào de shíhou, māma zài zuò fàn.
When I sleep, Mom is cooking.
verb + 的时候
我八岁的时候开始学汉语。
Wǒ bā suì de shíhou kāishǐ xué Hànyǔ.
When I was eight, I started learning Chinese.
time + 的时候
打电话的时候他不在家。
Dǎ diànhuà de shíhou tā bù zài jiā.
Sandhi:Dǎ diànhuà de shíhou tā bú zài jiā.
When (I) called, he wasn't home.
verb phrase + 的时候
3. Share a tip
的时候 always comes after the verb or time phrase — say 睡觉的时候, not 的时候睡觉.