Both kanji use the kun'yomi vocab readings. So, think to the words 右 and 利く to learn how to read this one. It probably reads like this because it's two separate words come together (right + handed) rather than one word.
My son is not right-handed.
Although I am left-handed, my mom bought a right-handed baseball glove by mistake.
I really liked her but I was turned off when I found out that she was right handed. I don’t know why.