Use a diagonal seam when joining strips to create the length you need for a binding strip. That makes your connection flatter and less bulky. It also makes the join 'disappear'.
|Place strips good sides facing. Sew a diagonal line.|
|Cut off the triangle leaving 1/4 seems allowance.|
|This is what it look like on the back after ironing.|
|This is what it looks like on the front after ironing.|
|Fold the bindings strip in half and iron.|
You can barely see the join.
The bulk of the fabric is 'spread out' so the strip lies flat.