Flat pack! I'm a reasonably practical type but they're frequently missing bits the instructions are shite and the materials cheap and flimsy.
I can't afford high end furniture so generally stick to 2nd hand or occasionally will splash out and pay someone to do it for me.
Knitting - I can knit a square, can cast on/off and do purl or knit (It does take a LOT of practice) but don't know how to increase or decrease or follow a pattern, plus how the hell does the "tension" thing work? If I'm knitting a square it's all even and only varies depending on size of needles and thickness of the yarn?! - if anyone can recommend a good easy to follow guide, possibly YouTube video with accompanying written instructions? I'd be tempted to learn this winter
Never tried crochet is it easier?
Learning an instrument or anything musical has always been a no go for me. sorry as this will be annoying but I'm the opposite here, I can get a tune out of almost anything! Musical instruments, household objects, stationery, body parts... totally useless skill though 
Not just maths but anything where maths is key, so working out how far away somewhere is on a map, calculating how much wallpaper or paint I need or understanding bookies odds or more complicated financial stuff beyond basic budgeting (which I am actually good at) I'm ok with arithmetic but as soon as it's anything beyond the basic 4 functions...nah!
Not a "gender thing" either I'm well aware girls and women can be and are excellent at maths and all related "stuff" cos my mum and sister among others are excellent, my brain just won't do it. I had to resit GCSE and even then I barely scraped a c even with intense lessons and a LOT of help from a friend who is now a Maths teacher and she hates when I ask her maths stuff even now, cos she knows she'll have to break it down to like 10 year old level!
@ImEatingVeryHealthilyOhYes dresses! Makes life much easier I discovered this trick far later than would have been helpful.
Also decide on a colour "palette" that suits you and styles and don't waiver WHATEVER is happening fashion wise. Fashion is fleeting, style is timeless (I think that's a quote but forget who)
I'm a short, fat, extremely white redhead (well fair bit of grey these days!)
I've had to accept willowy, boho styles and certain colours/shades simply don't suit me.
Ugh changing the bed! Even worse now I'm disabled! I have to pick a "good day" load up on painkillers and plan a day of rest the day after! As a result it doesn't get done nearly as often as I'd like! (And no I'm not admitting it here!)
I can do very basic "mum
Make up" (dds quote) but I cannot do liquid eyeliner and it be the same on both eyes - one will be thick and winged the other thin and basic - nor do I have the first CLUE what dds on about when she tries to explain modern make up, contouring etc to me - May as well be speaking in Russian!
@MrsMoastyToasty I can play insofar as I know the piece names and how they move but I am rubbish at thinking ahead and anticipating the other players moves and know nothing about the "posh" chess players you know when they give it "ahh yes that's the stravinsky gambit"
I'd love to know how to play poker too, my understanding is the hands effectively don't have a best or worst hand but it's more like Rock Paper Scissors where each hand can beat certain other hands but not all hands? Certainly wouldn't know how to discard or pick up cards if that's even how it works!
Height in metres and centimetres, weight in kilos omg yes! Even though I'm supposedly of the first Uk metrically taught generation I can estimate an inch or an ounce or a pound, really struggle with metric measurements
First Aid positions erm I think you need to explain?
Sudoko really? I do these to help me sleep. What is it you struggle with?
I can bake ok tasting cakes but utterly rubbish at the decorating stuff, even basic buttercream whirls elude me
Another here who struggles with clock change bollocks - just keep us on one time!
and making tablet there's definitely a knack to this! Mine is very hit and miss, my mum and my grans were perfect every time.
Driving and budgeting
Nothing major, then 
Rice - I struggle with that too, I'm now lazy and buy micro rice, despite not having a microwave - it can be reheated on the hob 👍