Super simple.
Supplies needed- Pencil, construction paper or 2 depending on the size of hands, white paper, scissors, glue stick and markers.
First we traced both my daughter's hands (that's why the hands don't lay exactly together). Cut both hands out. I drew line on each hand where her nails are so she could color each in. She had a ton of fun with that part, she was cracking up thinking it was the funniest thing to make "her" nails whatever color.
Cut a slice of your white paper, length isn't really a issue but think height needs to be a little bit smaller then the palm size.
Write your message. For the inside of our card we thought up sayings like "Happy (Grammy) Mother's Day!" and "Gift Good For Nail Day With Your Daughter," the language was a little goofy cause it was from all of us, but it made it extra special. As you see my daughter thought the inside should be just as colorful as the outside. She isn't at the writing stage (completely) yet, so I let her pick the markers. My only word of advice is don't sign card till the very end. If you wait till after the folding an gluing you can have signatures fill in the white gap easier. (The picture above was taken before my husband signed, hence the gap on right hand.)
Then fold accordion style. The 2 ends, first and last put glue on the back side (non-written) side. May need to adjust folding or chop extra when looking at it. Rub onto the palm of each hand, the non-color side, right should be your bottom hand and left be your top hand. Just think putting your hands together and opening them like a book. Now sign away!
Hope this gives you a idea for the next Mother's, Father's, or Grandparent's Day around the corner. :)