Glory be to God for dappled things – (line 1)
"Dappled things" has to be one of the more unusual endings to a clause that begins "Glory be to God." Our first mental associations for "dappled" might have to do with color, drawing, or painting.
All things counter, original, spare, strange; (line 7)
The poem becomes more general about what "dappled things" are as it goes along. Here the category widens to include anything that is "one-of-a-kind." The speaker is clearly most amazed by odd or unusual things.
Whatever is fickle, freckled (who knows how?) With swift, slow; sweet, sour; adazzle, dim; (lines 8-9)
Part of the poem's effect is to fill the reader with wonder not only about things that are unique and "one-of-a-kind," but also about things that seem commonplace. The coexistence of pairs "swift" and "slow" and "sweet" and "sour" is nothing new. That's the point – they have been around since the creation, but the creation was so incredible that we should still be awed by it.