well, first of all you have to know that you have to find 5 problems
now you can follow the hard way and invite interesting problems by your own or you can follow my tips
for Div2 A:
it's so easy just put a list of strings and assign a value for each of them and put a random question like find the sum of values of the strings that contain "Bombi-bombi" , "Dombi-dombi" or "Tombi-tombi" as a substring
no matter what the question is but try to make the problem required to copy things from the statement as much as it possible, so users can't solve it under 2 minutes

for Div2 B:
problem of leap years are very suitable for this level
put any random question of leap years so users should spend time reading about it in Wikipedia
and don't forget to make the pretest weak,so participants can waste their time on hacking and then only few number of users will solve all the problems(that's gonna make your round looks hard)

for Div2 C:
pick a random problem from any online judge and make a slight change on it
it's gonna be easy for you since this kind of problems are easy to change and easy to understand
so if the original problem ask for the minimum value make it for the maximum value or maybe you can make it for both of them (clever huh ? )

for Div2 D/E:
don't be afraid, even if you're a Newbie and you can't even understand the solution of that problem
it's alright buddy but you have to be careful
because all you have to do is to pick a problem from an online judge which hide submissions of solved problems
change the statement (not the idea or what is required) and you can use the solution and the code of one of the users
for more efficiency try to pick it not that famous, so users can't find it that easily

Finally:
no matter if you used the first way or the second, remember CF will pay you and will accept your problems magnanimously and you will get upvotes on your announcement
Note it's a very important step : after the round say sorry for CF community and tell them that you didn't noticed that they're a copied problems