Made some lemon slices at the weekend using this recipe.
Having now made them a few times, I can make them quite fast, though still have to follow the recipe carefully.
The biscuit base works well and can be used with other things. Getting the lemon custard right is key for these. The recipe calls for a lot of lemons, this time I only used two, but it seemed to work just as well. If you double the sugar, you get a more meringue type texture to the lemon custard.
They also work best served chilled. You can dust them with icing sugar, however I miss this step unless I am serving them to guests as storing them can then get messy.