Just run a bead of clear silicone around the edge and set sink in. For a little easier on hook up pre plumbing faucet and drain makes final hook up much easier.
A sink this small is not the norm but you can find sinks in this smaller size. I don't believe Glacier Bay has them but other companies do custom size sinks and sinks for smaller spaces. I'd suggest searching the internet for companies near you. Be aware these can be a bit pricey than a standard size available.
I measured my installed sink from outside to the outside of the rim and I get 16 1/2" front to back, and 20 1/4" side to side. The rough in hole is 15 1/2" front to back, and 18 5/8" side to side. A paper template comes in the box to trace a perfect oval hole onto the counter.
Hey Vince check in store or punch the word “ installation“ into the Home Depot site search bar. You will see options in the search results.
The sink is 17” front to back by 20” side to side. The inner depth is 6” and about 8” total depth
The distance from the center of the faucet to the front edge of the sink is 14” and inner edge of the bowl is 12”. The outside dimensions are 16.5” front to back and 20.5” side to side. The inner bowl dimensions are 10” front to back and 16” side to side. The depth is 6” from the drain to the top edge.
Inch and a quarter But it needs the ports for the overflow just under the rim
20 inches wide 16 1/2 deep
I have two of these sinks installed in my bathroom. The sink is 19 inches wide.