The time required to create a skills matrix depends on how you make it.
One method can be using Excel, where you manually list all the related pointers and skill information and create a fully custom skill matrix.
The other way is to input all the relevant information into a resource skills matrix software and generate a skill matrix.
For example, you need a software developers' skills matrix. All you'll have to do is:
Assess the skills which are required to complete a project successfully.
Evaluate your employees' skills and interests
Add the data into a table or a matrix
Map employees with the right skills
Use the skills matrix to identify training needs and allocate assignments