The standard way to create a master point for a two piece anchor is to tie a fixed loop in the runner, usually an overhand knot. This does makes a nice loop to clip your master point carabiner, but it has a couple of issues; one, it can be really hard to untie after it's been loaded, and two, it takes up a lot of the sling material, making it just about impossible to tie if you only have a 2 foot runner.
Solution: use a clove hitch at the master point.
Note that this is tied with a 2 foot / single runner. If you try to use a single runner to equalize two bolts like this by trying to tie an overhand not, it's not gonna work. With a clove hitch, it does.
Note - This is closely related to the technique of using a girth hitch at the master point, which we cover extensively at this tip.
MUCH easier to untie after it's been loaded
Yes, it’s redundant. If any arm of the sling word to be cut or fail, the anchor will stay together.
Uses less sling material, you can equalize two pieces of gear with a 2 foot / 60 cm / single runner
Easier to tie with gloves on, if you use the crafty technique shown on the video below
Stronger - compared to a loop knot tied in the rope, the clove hitch retains more strength
You can adjust the anchor if the primary direction of pull changes, which often happens after your second arrives at the anchor.
Here’s a nice Instagram video by AMGA certified guide Cody Bradford that talks more about this.
Need another endorsement? Hey, don't take my word for it, it's on the Petzl website.
Here’s a nice video showing a slick way to tie it, as shown by ACMG (Association of Canadian Mountain Guides) Guide Brent Peters. Pay attention to the subtleties of the technique. The initial clip of the carabiner needs to be gate up and in, not down and out. (Of course, you don't have to tie it with this fancy one-handed technique, feel free to tie a regular two handed clove hitch with the sling.)