Flat pack tray with curve on set-up and blank for forming the same

A blank of sheet material for forming a tray, the blank comprising:

• a plurality of panels hingedly connected in series, the plurality of panels comprising a top panel configured to form a top wall in a set-up tray, a first side panel configured to form a first side wall in the set-up tray, a bottom panel configured to form a bottom wall in the set-up tray, and a second side panel configured to form a second side wall in the set-up tray;
• a first locking arm flap hingedly connected to the bottom panel along an upper edge thereof and a second locking arm flap hingedly connected to the bottom panel along a lower edge thereof;
• wherein the first and second locking arm flaps are configured to be secured together to form a locking band in the set-up tray, the locking band extending across said top panel and holding an underlying portion of said top panel in face-contacting relationship with said bottom panel;
• wherein the set-up tray is configured to transition from a first configuration in which said set-up tray is substantially flat, into a second or erect configuration in which said top wall defines a concave surface configured to hold in place a curved item;
• wherein said set-up tray is configured to be transitioned from said first configuration to said second configuration by sliding said top panel relative to said bottom panel.