I was requested to make a cake resembling this. My question is, the bottom tier, the star, could it be a 12 inch round and then a few square cakes baked and cut to match the sides of the round cake or do any of you think it's a pan? Any suggestions or ideas are greatly appreciated. I was trying to find out who the originator of the cake is so I could ask them how they went about making the bottom tier.

It may be the Wilton Star pan

I agree.  probably a star pan.  Or if you don't have or want to buy the pan,  I would make a large circle that would contain the star you want within it, and carve away the five pieces to make the star shape.  You could start with a small circle and attach the arms, as you suggested, but I would worry about how structurally sound that would be.  

it would be structurally sound the way you described piecing it together -- there's nothing on top of the joins and even it there was it'd still be ok -- just glue them together with icing -- perfect -- no worries

I really doubt it is the star pan -it just is not big enough to be holding those upper tiers.  I would make a round and cut sq cakes into points as you mention.   Using b'cream to hold them together it will be stable as long as the whold 'star' if pervectly level & supported before adding the upper tiers..... BUT then..... it will depend on how many servings you need for the overall cake. Makes little difference if you need 50 servings that I'm guessing those upper tiers are a 9" & 6".  

That bottom tier just doesn't look like a star to me.  It looks like a square tier with the sides cut in.  I don't think you have more than 4 points there.

cakefan you are very observent :)  Could be a sq w/sides cut in or a round w/points added.

I agree with cakefan92, it looks like four corners to me, almost like a pillow pan without being rounded on top.

You know, I just looked closer at it after I read your comment. I'm going to see if I can find the originator of this cake and/or possibly get other angles of it.

The shape appears more like this pillow pan with the top flatten.                                                                                                                                                                         https://www.amazon.com/Janolia-Aluminum-Baking-Dessert-Chocolate/dp/B07GB989FZ/ref=sm_n_au_dka_US_pr_con_0_0?adId=B07GB989FZ&creativeASIN=B07GB989FZ&linkId=fe89b7efd22206fcbd345393cdf217b8&tag=cakecentral-20&linkCode=w41&ref-refURL=https%3A%2F%2Fwww.cakecentral.com%2Fforum%2Ft%2F848925%2Fstar-shaped-bottom-tier&slotNum=0&imprToken=xwXNTN3lr2xfCkhd6pZ8WQ&adType=smart&adMode=auto&adFormat=grid&impressionTimestamp=1545493126970&tag=cakecentral-20

I've not seen that pan before but it sure does look like that bottom tier in the pix OP posted.    BUT......that link you posted does not say how big the largest pan  is.  Is it big enough to stack a 10"er on it? 

I have no idea, Lynne.  It showed up as an advertisement below this page.

I actually have this pan at home, I don't like the way the corners bake so I really don't use it. I think I'm going to print out a star probably 16 or 17 inches, tape the paper to make it the shape I need and use it as a stencil. So I'm thinking a 12 inch round and then I can make the points out of sheet cakes that I'll make and frost them all together carefully.

Sandrasmiley is correct. That looks like a pillow pan flattened.

Thank you, I’m just hoping it sticks together and the edible image doesn’t rip. 

The entire cake is to feed approximately 80 ppl. So the base I’m thinking 10 or 12 round.