3-D Valentine's Day Illustrated Cards
Source: Martha Stewart
If planning to mail the card, measure the envelope first and size the card accordingly (usually about 1/4 inch smaller all around). For the cleanest results, cut the paper with a craft knife on a self-healing mat (cut straight lines along a ruler). Some cards need the additional backing to conceal cuts or add weight; create a border by cutting the back piece slightly larger than the base, and layer patterned and solid papers.
For train, snip flaps off envelopes, and tape envelopes to the flat beds.