The Borders plate provides one way to decorate your envelopes. Another way though, is to use the Adorning Accents Edgelits and matching embossing folder, to achieve a similar result, with the addition of the Big Shot.
Step 1 – Use the wavy Adorning Accent die to trim away the plain edge of the envelope flap, cutting as close to the edge as possible to retain the maximum amount of gum for sealing the envelope closed.
Step 2 – Line up the edge of the envelope flap within the Adorning Accent embossing folder leaving an approx. 1/4″ between the embossing the flap edge. (Tip – place in the embossing folder with the SU! and Sizzix logos face up for an embossed (raised) effect).
Here’s a close up of the die cut and embossed envelope flap.
Edited to say – By the way, the base envelope is the Crumb Cake Medium envelope (107297) and it isn’t the standard C6 size, so please bear that in mind when designing the card to go inside it 
I’ve added a tutorial for creating your own square seal envelopes with the Scoring Tool.
This is all very easy on shop baught envelopes with an oblong closing flap. But how would this work on an envelope made using the SU score board which results in a triangle flap?
regards
tania
Hi Tania
I’d suggest either:
– making the envelope in the oblong closing style instead of the triangle flap style and trimming as I did here (but you do get more paper wastage); or
– trimming (very thinly) along the two straight open edges of the triangle flap (in fact I’d cut the envelope with a little extra here to allow for it).
I will try to have a go and show you what I mean but it may be another week before I can get to it 🙂
Sara xx
I’ve now added a free tutorial for creating your own square seal (rather than triangle seal) envelopes using the Scoring Tool.