3 sentences

1. 请把邮票粘贴在信封的右上角。

   qǐng bǎ yóu​piào zhān​tiē zài xìn​fēng de yòu​shàng​jiǎo.

   Please paste the stamp on the upper right corner of the envelope.

   Source: Dong Chinese Dictionary

2. 请在表格的右上角填写该文件的字号。

   qǐng zài biǎo​gé de yòu​shàng​jiǎo tián​xiě gāi wén​jiàn de zì​hào.

   Please fill in the document's reference number in the upper right corner of the form.

   Source: Dong Chinese Dictionary

3. 他在信封的右上角盖上了一个当天的红色日期戳。

   tā zài xìn​fēng de yòu​shàng​jiǎo gài​shàng le yī gè dāng​tiān de hóng​sè rì​qī​chuō.

   He stamped a red date stamp of the day on the top right corner of the envelope.

   Source: Dong Chinese Dictionary