Is it common to create your own compound signs?

For example, if i were signing “… PENCIL PRECISE” (not the full context), would it be fine for me to start the movement of “PENCIL” at my mouth and go straight into the sign for “PRECISE”? Or is this like making up a word and it wouldn’t be understood?

I’m not sure if there’s rules to compounds and contractions or the exact difference between them, but I’ve been super interested in them recently.