FAQ
Java: Textures Folder
Jokes aside, textures need to be anywhere inside the "YourPack/assets/minecraft/textures" folder inside your pack. If you are in 1.19.3 or newer they need to be in textures/item or textures/block.
If you are using the downloaded version of Blockbench, make sure you also load the textures from the correct location into Blockbench (or save textures from BB directly there), or the relative texture path inside the model will break.
If you are using the web version you need to rightclick every texture and specify the folder path (after "textures") and name of every texture manually instead.
If you wanna use custom subfolders in 1.19.3 or newer use !faq java-1.19.3-textures