"Stack" sounds like "dack."
"Stick" sounds like...
"Block" sounds like "bock."
"Clock" sounds like... At a party featuring all adults but one other child, he surprised a room full of young, unmarried men and women by shouting "Cock! Cock! Cock! Cock!" No rooster in sight, eyebrows were raised until I agreed, "Yes, that's a clock on the wall."
Early on, he got the 'x' sound, but then lost it and replaced it with a 'k' sound. It made the word "fox" sound like... Luckily, the 'x' sound is back.
Oh, and is favorite food is "taw-kit". Can you guess what that is?