The counter is your enemy. Get behind it and you're selling across a barrier, and a barrier turns help into a transaction that stalls the sale.
That's true in every store, and it's a special problem in businesses built around counters, like jewelry and photography, where associates spend whole careers with a barrier between themselves and every customer. But don't give up hope.
Try this with a coworker. Stand 3 to 4 feet apart, facing each other. One of you holds up a piece of paper and describes it like it's merchandise. The words don't matter.
Now move in close and turn shoulder to shoulder, at a slight angle. Same paper, hold it out in front of you both and describe it. Feel the energy difference?
Face to face feels like a transaction, one of you selling at the other. Side by side feels like two friends figuring something out together.
One position is sales-y. The other is natural.
That's the whole principle: selling from the side puts shoppers at ease, and people at ease buy more. Face to face across a counter grants authority. Shoulder to shoulder is a buddy helping you decide.
So find ways around the barrier. Come out from behind the counter to show the piece. Walk the item to where the customer stands instead of summoning them to you. When they've chosen something, set it on the counter from the front, from their side, and keep the conversation going, because stepping behind the register announces the sale is over.
The counter has its place, and it's narrow. Greet from it, keep high-value pieces secure while you pull them, and ring the sale on it. When the store is slammed and you're covering three cases at once, standing guard is the job. Outside those minutes, step around it. A locked case is not a selling position; it's stock you happen to stand behind.
Selling is nothing more than the transference of feeling. I feel good about this piece, so you feel good about it. Feelings don't transfer well across a barrier, and they transfer beautifully standing side by side. Get rid of the furniture between you and the customer, and watch what happens to your closes.
Come out. Behind the glass you're an authority granting an audience; beside the customer you're two people looking at the same piece with the same goal. Stay behind the case only to greet, to keep high-value pieces secure while you pull them, and during a rush when you're covering several cases. The rest of the sale happens on the customer's side of the counter.