I often like doing something similar on small art pieces where a border is planned. Yesterday I finished painting a holiday art piece I began in a demo some months back. (I just can't toss a demo) I must finish it. Here's what I'm going for... then I'll show you how to achieve a perfect 1/4 inch fillet of fabric.
In this example... I wanted a soft mid value mottled teal which I did not have. Since I own almost all the inks imaginable, I used Tsukinekos all purpose ink # 93 (blue bayou) to permanently change the color of 1" strips of this slate blue batik I did have. In a small container, I added a wee bit of water to straight ink.. dipped the precut strips, withdrew them and allowed them to dry overnight atop plastic.
Once heat set by iron on a cotton setting... the 1" sashing is added round the central image. Yes this is larger than the end result calls for but stay with me.
In this step we are adding the final border leaving a precise 1/4 fillet of the batik in view. I cut the final border a wee bit wider than ultimately planned ( 4" width likely to be cut back to 3")
The trick to this precision is working from the back and using the edge of your 1/4 foot to gain precision. The darker border is placed right sides together with it's edge lined up with the 1" lighter teal strip. It's unseen here... but is basically a straight seam. The left edge of the pressure foot is guided by the stitch line of the original lighter teal 1" strip.
After adding the 2 side borders... the top and bottom borders go on but call for using a ruler to premark( again working/marking on the back side of the quilt top) where to guide the left side of the pressure foot so that the stitch line will meet the spot where batik begins... all this to guarantee a precise 1/4" fillet on top and bottom. Don't try to eyeball this step... You'll likely be sorry.
Now press top and bottom and get ready for the quilting process. You will note I haven't cut away any excess seam allowances. To my thinking... what's there seems to add stability to this small quilt... so I'm leaving it all there.
Back to the front and here's what we get! I'll pin this piece to take with me to Lake Tahoe in a week... A whole week of quilting small pieces I have been holding on to. This little piece will either be sold ( holler if you want) or be donated for a fundraiser. I've donated 3 pieces to organizations this year so I'm okay with selling this one (or another similar already finished) if you're interested. Comment or email me at email@example.com.