Informal leave letters are generally written to our friends, colleagues, to our parents, loved ones or our partners. So, informal letters can be written like your wish and there is no such perfect template for informal letters. But, since it is a letter, a common general format is described so that it gives a clear picture of what it says. Take a look at the template below.
Address of the recipient.
Dear [Name of the recipient],
Content of the letter.
Yours lovingly, friendly, etc. depending on the content on the letter.
Name and signature.