now you may (or may not) be thinking...I have corners! help!!! no fear, there's an easy happy way to doing them cleanly.
and it's not this. picture of my first sewing project (Kamui jacket)...the stitching is way too tiny to make bias tape look nice (it's usually better to use a larger stitch for topstitching), and I just attempted to tuck the corners down, which doesn't work too well, because a) it looks kind of sloppy b) it's very difficult to simultaneously nail the back flap of fabric as well. luckily, there's a better way!
How to make your corners look awesome
I'd recommend doing a trial run first using a marker. Once you're used to it you can go without. Take your bias tape, line it up, and mark where the seam will be on your fabric corner.
Do this from the other direction as well.
take your bias tape and stitch along the fold line.
stop at the intersection you just drew~
for the next step, you'll want to take the side of bias that's not stitched down and fold it along the corner. match it to the top (if you're doing a 90 degree corner, anyway), and more importantly, to the side so that it's even.
stitch until the intersection, just like you do with the other side.
it should look like this on the back side. precision is key! if it doesn't match up, it's okay; just tear your stitching out and try again.
keeping your fabric folded the way it was when you did your second line of stitching, draw a horizontal line across the fabric that matches up with the first line of stitching. after you do this, draw two diagonal lines up and down to form a triangle.
fold the rest of the fabric except for your bias tape away from your triangle.
stitch the corner fold in, using the lines of your triangle as a guideline.
check the fit if you like, then trim the excess fabric away.
fold your bias tape over the corner. you might want to use a point turner of some kind to make sure that the top is nice and crisp. it should look like this on the front.
and like this on the back~
at this point, you need to do something to secure the back. you can:
a) stitch through it
b) stitch in the ditch as shown above (provided you're using overlapping bias tape)
c) slipstitch it (prettiest method, but most time consuming)
d) slipstitch it then topstitch it (for extra precision)
e) fabric glue/stitch witchery
slipstitching is like this. there's more tutorials elsewhere, but you essentially pick up a little bit of your fabric with your needle, then a little bit of your bias tape along the fold, and then pull it tight. if you're using only one layer of fabric, you'll have to pick up your fabric from inside the bias tape. if you're lining it, or have more than one layer of fabric, you can catch it to the lining on the other side of the stitching to make it invisible as well.
slipstitching will usually give you the best results. as you can see, the front of my umi waist cincher looks more or less the same on the front (seen on the left) as it does on the back (two strips on the right).
it also looks pretty decent from really closeup, too. having no visible stitching at all (well, except for the satin stitching, haha) makes it look really crisp/clean.
here's a finished invisible corner.
and the same from the back side. it looks great on the inside too! no worries about people seeing the inside of the fabric pleats as they ripple down. (silly umi skirts)
but wait! there's one more way of doing things.
shit!!! I'm out of time method
pros: only good if you're mowing down bias tape cause you're in a time crunch
cons: can't do your first line of stitching along the fold.
fold your bias tape in half back on itself. stitch a triangle this way for an outwards corner.
or like this for an inverted corner.
clip away the excess fabric, and you'll have this. see how one opens one way, and the other the other? the other methods are better though since they're a bit more precise, but I figured I'd throw this in here anyway just in case.