Aloha, I have made many top note quilt cards.
I have several samples in my gallery:
Splitcoaststampers Member Galleries - stampindoe - Handmade Cards & Crafts
To answer your questions:
I adhere all the squares to Whisper White card stock with a glue stick. After gluing all the pieces on, turn the whole thing over and rub the back of the Whisper White piece to stick the front pieces down really good. I usually add some ribbon or buttons which do require more postage.
Good Luck with your project.