ずっと昔から工作は得意なのさって英語でなんて言うの？

*I have always been a handyman since I was little.- A handyman is someone that is good at repairing and making things inside or outside the house and who does this in his own home or as a job. This means that you have always had it in you to fix things.

Informally, we may say that we are 'good with our hands' if we: play the piano or violin, fix cars, knit, play pool, make sculpture or paint beautiful pictures - or do anything using hands which the majority of people find difficult.
Being good with one's hands is sometimes known as 'manual dexterity.'
Manual dexterity is the ability to make coordinated hand and finger movements to grasp and manipulate objects.

Being good at doing things by yourself at home, such as repairing broken things, manufacturing your own things from scratch, in other words, D.I.Y. or 'do-it-yourself', it can definitely be a feather in your cap (an achievement that you can boast of). It is something you can boast of because having to hire handymen or having to run to the shops to go and buy a new item all the time can be expensive.
So, you may say:
Since I was little, I have always been good at D.I.Y. (do it yourself).
or
I am .so good at D.I.Y. (do it yourself) because I have done it since I was little.

"I've always have had a knack for fixing or building things."

You use this expression to let everyone know that you have always had a "special skill or aprtitude" with fixing or making things. This is why you would use the word "knack".

Arts and crafts, construction, making things, etc are all technical skills that one may acquire. Therefore, you may say you're good with your hands or you're pretty handy at fixing things. It all conveys canvas the same message.

Any fact that was true in the past and is still true today, needs to use the present perfect form of have/has been: "Since I was little, I have been good at fixing things." One can be "handy," "crafty", "have manual skills," "good with his/her hands". If one is good with their hands it means they have manual skills and can be good at creating, fixing, building things, adjusting things or anything people tend to do using their hands.