I am going to post my letter later.
Later, I will eat a sandwich.
give a sentence using the word 'to check out'
I can't imagine using it at the start of a sentence. I'd move it to later in the sentence.
One sentence using all the letters in "these letters" could be: "Settle these letters on the shelf for later use."
the atheist later became a scientist :)
Let's get together for coffee later.
You are scheduled to take an aptitude test later today.
I need an acceptance letter.
Yes.
Tell me who wrote the letter!
i shall decide wether or not to go to the shrine later.
The first words of my letter are for you.