Can I build a grip with wood the customer supplies?

Yes.  As long as the customer realizes the wood must be of a suitable size and cured (dry) not green. Also I do occasionally mess up a grip blank and have to start over so do not send me something irreplaceable to build a grip. I will do my best to replace any wood I mess up but I can’t replace an heirloom. (Yes this sounds silly but it is surprising what some people will ask for).