Can someone confirm below translations please. I can speak good Irish but not good at grammar

'Top of the bottom'........Barr an toin
'Bottom of the bottom'......Iochtar an toin or bun an toin
'The wee field'....... An gort beag

It looks silly but 'the bottom' is the name given to a field going back a long time in the family and now under forest. I am erecting signs for forest paths and need the correct grammar especially the genitive!

barr na tóna

bun na tóna (I'd prefer "bun" here. It seems it's used quite commonly.)

Tóin is also used for "ass", by the way, so some word play is possible.

The last one looks OK.

My response was on the way when the prior one was posted, but I'll post it anyway.
The word tóin is feminine in grammatical gender, thus the changes below. You could also use bun, as you did in one case (it is masculine in grammatical gender), since tóin could be understood as referring to the buttocks. The word íochtar (also masculine) would refer more to the lower part of something, but any of the three could be used. Note the fada on the "i" in íochtar.

barr na tóna [tóin in the genitive case]
barr an bhuin [bun in the genitive case]
barr an íochtair [íochtar in the genitive case]
top of the bottom

bun na tóna
bun an bhuin
bun an íochtair
íochtar na tóna
íochtar an bhuin
Bottom of the bottom

an gort beag
the wee field

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I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.

Many thanks for the choices and correct grammar. All three I think could be used and have been in Irish placenames, but I think I'll go with toin. Its mostly used as a describing word but there is a 'baile na tona' in Cork and a 'doire na tona' in Cavan https://www.logainm.ie/ga/s?txt=gls:147-t%C3%B3in

I can confirm tiomluasocein's work above is good.

(CaoimhínSF's offerings are also good with Labhrás' corrections but you've already indicated going with tóin and I agree with your choice.)

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).