1. Most difficult or annoying to handle, adjust, or deal with; requiring the most fussy attention to detail.
Usage: superlative form of 'fiddly'; informal; chiefly British

Examples

• The fiddliest part of assembling the furniture was connecting all the tiny screws.
• Sewing buttons on a shirt is one of the fiddliest household tasks.
• The fiddliest aspect of the recipe is tempering the chocolate correctly.
• He found the fiddliest work to be adjusting the microscope's focus.
• The fiddliest step in the instructions required steady hands and patience.