Here's what I made for a 4x6 envelope.
Used white, black and red card stock paper. Didn't have gray card stock so settled for some grayish paper. Sticky Doos glued the buttons in place to have a "floating" look. A black yarn served as the wire that I looped inside the card and secured at the back with a tape.
For the "happy birthday" message inside the card, I used the Cricut. I used the midnight blue card stock for this with the tag pattern. You can see the "controller wire" snaking through at the bottom right.
Cricut cartridge "Plantin Schoolbook" was used for the "happy birthday" message.
The card needs improvement but not bad for a rush project. :-)