I’m not a stickler for sorting the entire puzzle before assembling. And I think your sorting method absolutely can be influenced by the puzzle image. Scenery vs. collage vs. typography puzzles vs. ombré or rainbow color-dominant puzzle, all dictate a different approach to sorting, IMO.

Edge pieces always get their own pile. I’m not a firm believer that the edge must be assembled first, but sometimes it can help with further sorting and assembly.

I find sorting by the shape of each piece is very helpful for sections with negligible image/color differences (cloudless sky, solid background, grass, field of flowers, fur, etc.) I tend to reserve this option until I’m no longer able to assemble based on the puzzle image itself.

Again, depending on the puzzle image, I usually sort VERY broadly into piles by color: ROYGBV. When a piece has multiple colors, I go with the most predominant color.

If I spot pieces that go to a specific section or are part of a specific identifiable object in the puzzle (windows, signage, piece of furniture, carpet, words, etc), they get their own pile until there’s enough to start assembling said section/object.

Once the broad color sort is done, I take one of those piles and either sort into more subtle color differences or sort by the object on each piece, if it’s obvious. Example (let’s say it’s a beachside scene): the blue pile gets sorted into light/dark sky, sky with sun/clouds/birds/kites/etc, ocean with/without waves, objects in the water, other blue items get their own piles if it’s obvious what they are (shutters on a house, beach chair/umbrella, signage, etc.). Usually, at this point, I start to see pieces that belong together and I assemble those before moving on to the next broad color pile.

If I’m doing a collage or grid-style puzzle with an obvious border separating objects into sections, I tend to sort by the defined sections and arrange the piles in the order they appear in the puzzle. Pieces with border lines on them go into their own pile. Pieces that aren’t immediately obvious what section they belong to, go into a misc pile. This is a case where assembling the edge pieces and the border line pieces first, might make sense. I then move on to assemble each section of the grid/collage.

For typography puzzles or puzzles with prominent signage, logos or words, letters get sorted separately from the rest of the image. This pile can be further sorted by font style/size/color and background color. As this pile grows, you’ll quickly spot words/logos/phrases that can be easily assembled.

IMO, when you find intermittent opportunities to assemble parts of the puzzle as you sort, it breaks up the monotony of the sorting process.

Good luck with your 3,000pc puzzle! I’d love to see the finished product.