Personally I like to establish a routine with my new gliders. A daily ritual.
I take the sleep pouch out of the cage, I don't use cubes because new to you gliders are crabby usually and it's difficult to get them out of those small entry hole type of pouches. I use sleep pouches with a wide open top that I can flip inside out if need be.
I take the sleep pouch out of the cage, and offer them a bonding bag. I manipulate the bottom of the sleep pouch with one hand to encourage them to want out of it, and want into the bonding bag. I don't mean roughly, just wiggle your fingers underneath the glider from the underside of the pouch. After a day or two of this they see the bonding bag and just walk into it.
It may take you longer than a day or two and that's fine, don't put a time frame on things.
I do this at the same time, everyday, so the glider starts to understand that when I open the cage at that time, this is what is going to happen. They learn the routine quickly.
IF for some reason this method doesn't work. holding the underside of the pouch push the glider up to the top of the pouch so they are more exposed then offer the bonding bag, they will likely dive right in it.
There is another method, but unless I see your bonding bag I don't like to suggest it. Pictures help
As I mentioned abouve, personally I would remove the cube until your gliders walk into the bonding bag when it's offered. Those cubes can be frustrating and cause undue stress when in the early stages of building your friendship with the glider.
The goal is to show them you can be trusted, you respect their cage, pouch, them as individuals. Fumbling with a cube or hidey pouch kind of defeats the purpose, make it easier on yourself and them. Use pouches that are easy for you to handle and get them out of.
I rarely just pick my gliders up and put them in a bonding bag, they have legs, and I like them to go into whatever I offer them on their own terms, rather than me forcing them. Now I can offer them anyyyyyyyyyyyy kind of pouch, bonding bag, bonding scarf, whatever it may be and they all walk into on their own. Less stress on me and them.
Take your time, you will find what works for you and them.