How to create element for hours x rate

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I'd be grateful for advice on what I need to do for creating a new element. I've had a look a the product papers and have seen what's needed for the actual element creation itself, but I think there are further steps required in this scenario e.g. creating calculation value definition and FF, but I'm unsure and cannot find guidance on that.

The requirement I've got is for an irregular earnings element that is taxable and subject to NI contributions (UK Payroll). In the element entry we need to be able to enter the number of hours/mins worked and for this to be multiplied against a flat rate of £8.16 per hour. So far, I've created an element and a Calculation Value Definition with 8.16 as a flat amount. Then I updated the Element, adding the Calculation Value Definition under 'Calculation Factor' (with Calculation Step set to 'Rate Amount'). I was able to add the Element Entry to an employee but nothing