Screen design is forgiving. A colour is slightly off, you push it. Type is a little tight, you fix it after launch. Nothing is ever really final.
Packaging is not like that. At the end of the process a machine makes several thousand identical copies of your decision, on a physical material, and none of them can be edited afterwards. That single constraint changes how the whole design has to be approached.
The dieline comes first, not last
A dieline is the flat template showing where the material gets cut, folded, and glued. It is not packaging around the design, it is the canvas, and it should be in place before anything is laid out.
Designing a beautiful front panel and then trying to wrap it onto a structure is backwards, and it produces the classic failure: artwork that lands across a fold, or a logo that disappears into a glue flap. Panels also are not equal. There is the one that faces the shopper, the ones seen at an angle, and the one nobody sees. Knowing which is which before you start is what stops the important information landing on the wrong face.
The surface is rarely flat
A bottle curves. A tube gets squeezed. A pouch creases wherever it likes.
On a cylinder you lose the edges of the label to the curve, so the usable area is much narrower than the artboard suggests, and anything centred by measurement will look off-centre in the hand. Type set across a curve distorts. These are not rendering problems to fix in the mockup, they are layout constraints that belong in the first sketch.
Colour shifts on the substrate
The same ink prints differently on coated stock, uncoated stock, kraft board, and foil. Uncoated absorbs and dulls. Kraft adds a brown cast to everything, so a clean white becomes cream and a soft pastel goes muddy.
This is why a palette specified only in hex is not a finished palette. Print values need to be specified alongside, ideally with a spot colour where the brand colour genuinely matters, and ideally checked on the actual material rather than on a desktop proof that is lying to you politely.
Small type is the first thing to fail
Ingredients, directions, warnings, weights. It is the least glamorous part of the layout and the part most likely to get the product rejected.
Small type has a floor that depends on the printing method, and below it strokes fill in and the text becomes genuinely unreadable rather than merely small. Reversed-out small type is worse, because ink spread closes the letterforms from the outside. If the layout only works by setting the legal copy a point smaller than the printer's minimum, the layout does not work.
Legal copy needs a home from the start
Barcodes, net weight, ingredient lists, recycling marks, importer details. None of it is optional, all of it arrives late, and it is almost always more than anyone estimated.
Designing the pretty version first and then trying to find somewhere to put a barcode is how you end up wrecking a back panel in the last week. Blocking out generous space for it at the start costs nothing and saves the layout.
You get one chance per run
Everything above comes back to this. A print run is a commitment measured in thousands of units and real money, and the cost of a mistake is not an afternoon of rework, it is the entire run.
That is why packaging work is slower and more checked than screen work, and why it makes you a better designer generally. It removes the option of fixing it later.
It makes the rest of the work sharper
Constraints this hard change how you design everywhere else. Once you have had to make a mark hold up at small size, in one colour, on brown board, you stop drawing marks that need ideal conditions.
You can see the difference across two very different products in Skinhance, a clean skincare system built to feel premium on a shelf, and Crimson Red, a cranberry ale where the label had to work wrapped around glass. Packaging is usually part of a wider brand identity project, because the two constrain each other.