Is it possible to create the flavour of a food by using the component chemicals?

It's a little hard to understand exactly what you're asking, but flavor and fragrance scientists have been at this for a long time, and yes, there are people who specialize in flavor research, using methods like "collecting headspace" (gathering flavor compounds) and analyzing those with techniques such as gas chromatography. They work to figure out what the "most relevant" compounds are in a particular food. Seasoned professionals are usually able to recognize and name specific flavor compounds by smell.

But with a few exceptions, most of those chemicals aren't super easy to just buy off of a shelf somewhere without consulting with IFF or a similar company. (You can buy artificial vanilla, for example, and methyl anthranilate, the dominant flavor from concord grapes used in artificial grape flavoring, as a bird repellant). So for most of us without labs for fermenting synbio vanilla, we will find it more cost effective to use the original ingredient.

Most foods have hundreds of distinct flavor compounds and fooling the tongue, and especially the nose, isn't super easy. But it can be done in some cases, sure. It's worth noting that a great portion of how we experience flavor comes from texture in addition to the flavor compounds, however. Even when you buy a flavored chip that is meant to taste like steak or mango salsa or whatever, you'll often find it a bit off, perhaps the food industry's equivalent of the "uncanny valley" problem, thanks to texture and context differences.